Mosaic: Images from Tesserae, From Roman Floors to Byzantine Domes

The floor of the House of the Faun in Pompeii has a picture of Alexander the Great fighting Darius III at the Battle of Issus. It is not a painting. It is not a fresco. It is made of roughly one and a half million tiny stone cubes, each less than a centimeter across, set into mortar. You can walk on it. The image has survived 2,200 years of foot traffic, volcanic ash, and excavation. No painting from antiquity has endured like that. Mosaic is the most permanent image-making technology humans ever invented.

Mosaic is the art of creating images by setting small pieces of material, called tesserae, into a bed of adhesive mortar. Tesserae can be stone, glass, ceramic, shell, or any durable material that holds its color. The technique is ancient, durable, and architecturally integrated in a way that painting is not. A mosaic floor or wall is part of the building it decorates. It does not hang on the wall. It is the wall.

This entry covers how mosaics are made, where the technique came from, who produced the greatest examples, and what to look for when you see one in person.

What Is Mosaic and How Does It Work?

A mosaic is built from the bottom up. The foundation is a series of mortar layers, typically between two and four, following specifications laid out by the Roman architect Vitruvius in De Architectura (c. 30 BCE). The lower layers are coarse, made with larger stones and rubble mixed with lime. The upper layer is finer, a smooth bed of lime mortar into which the tesserae are pressed while the mortar is still wet. Once the mortar sets, the tesserae are locked in place permanently.

The tesserae themselves vary in material depending on the period and the intended location. Floor mosaics in the Roman world used stone: marble, limestone, terracotta, and locally available colored stones. Wall mosaics, which needed to catch light and create luminosity, used glass. Glass tesserae are made by adding metallic oxides to molten glass, producing colors that penetrate the full thickness of the cube. Gold tesserae, a hallmark of Byzantine wall mosaics, are made by applying gold leaf to a thin sheet of glass, then sandwiching it between the gold and a second thin layer of clear glass. The result is a cube that reflects light from the gold surface while protecting the leaf behind glass.

A 2024 study published in the journal Heritage analyzed glass tesserae from the apse mosaic of the church of S. Agnese fuori le Mura in Rome, dated to the 7th century CE. The research used scanning electron microscopy, electron probe microanalysis, and X-ray powder diffraction to identify the chemical compositions of the glassy matrices and the coloring and opacifying techniques. The results showed a mix of newly produced tesserae and recycled Roman glass, revealing a complex production chain in Early Medieval Rome where glass was both freshly manufactured and salvaged from older buildings. Read the full study at MDPI Heritage.

A separate 2025 study published in npj Heritage Science analyzed mosaic mortars from the Roman, Byzantine, and Early Islamic periods at Gerasa (Jerash) in Jordan, covering roughly 650 years of production. The research found that early Roman mortars were of the highest quality, with careful selection of stone for both lime and tesserae, and distinct differences between layers. Byzantine and Umayyad mortars showed variations in lime content and porosity, reflecting evolving production traditions. Read the study at Nature.

Origins and History

Mosaic has existed for at least 4,000 years. The earliest known examples are pebble mosaics from Mesopotamia and the Aegean, dating to the 3rd millennium BCE. These used uncut river pebbles set in mud or plaster to create simple geometric patterns. The technique was limited by the natural shapes and colors of the stones.

The Greeks refined pebble mosaics into an art form. By the 5th century BCE, workshops in Pella and Olynthus were producing sophisticated figural mosaics using naturally colored pebbles arranged to create shading and depth. The Stag Hunt Mosaic at Pella, signed by the artist Gnosis, dates to around 300 BCE and shows a level of detail that approaches painting.

The innovation that transformed mosaic was the cut tessella. Instead of using natural pebbles, workshops began cutting stone and glass into uniform cubes, typically 1 to 2 centimeters square. This allowed for precise color control, tighter joints, and finer detail. The Romans called this technique opus tessellatum, and by the 2nd century BCE it had become the standard for floor decoration across the Mediterranean. Roman mosaics covered floors in villas, bathhouses, temples, and public buildings from Britain to North Africa.

The Roman Empire produced mosaics at industrial scale. Workshops traveled with the legions, decorating military installations and provincial villas with standardized patterns as well as custom commissions. The Alexander Mosaic from the House of the Faun in Pompeii, dated to c. 100 BCE, is the most famous Roman example. It depicts the Battle of Issus (333 BCE) with a level of pictorial sophistication that suggests it was copied from a Greek painting, possibly by Philoxenos of Eretria.

Byzantine mosaic represents the high point of wall mosaic. Beginning in the 6th century CE, Byzantine artists covered the interiors of churches with glass tesserae, creating luminous images of Christ, the Virgin, saints, and emperors that covered entire domes and apses. The mosaics of Hagia Sophia in Constantinople (dedicated 537 CE), the churches of Ravenna in Italy, and the monastery of Hosios Loukas in Greece represent the peak of the medium. Gold backgrounds became standard, creating a weightless, immaterial space that rejected the naturalistic settings of Roman art in favor of a spiritual, otherworldly environment.

A 2025 study published in Heritage examined glass tesserae from the Rotunda in Thessaloniki, Greece, one of the most significant Early Christian wall mosaic assemblages. The research used UV-Vis reflectance spectroscopy, SEM-EDS, and X-ray diffraction to analyze 36 tesserae in blue, green, yellow, brown, black, gold, and silver. The results showed similarities with other Early Christian and Byzantine wall mosaics in the use of colorants and opacifiers, including cobalt, copper, iron, manganese, and tin-based compounds. The study confirmed that the Rotunda's assemblage reflects the transition from Roman glass traditions to Byzantine glass production in the 4th and 5th centuries. Read the study at MDPI Heritage.

Key Sites and Practitioners

The Workshops of Pompeii (c. 100 BCE)

The Alexander Mosaic from the House of the Faun is the pinnacle of Roman floor mosaic. Measuring roughly 2.7 by 5.1 meters, it depicts Alexander on horseback charging the Persian king Darius, whose charioteer whips the horses to flee. The composition uses dramatic foreshortening, deep spatial recession, and a level of tonal modeling that rivals painting. The tesserae are stone, cut to roughly 0.5 centimeters, with some areas using even smaller cubes for facial details. The mosaic is now in the National Archaeological Museum of Naples.

The Mosaicists of Ravenna (5th-6th century CE)

Ravenna, on the northeast coast of Italy, was the capital of the Western Roman Empire in its final decades and then of Byzantine Italy. Eight UNESCO World Heritage sites in Ravenna contain mosaics from this period. The Basilica of San Vitale (consecrated 547 CE) contains the famous panels of Emperor Justinian and Empress Theodora with their retinues, executed in glass tesserae with extensive gold. The Mausoleum of Galla Placidia (c. 425 CE) has a ceiling of deep blue tesserae studded with gold stars, creating the effect of a night sky. The Basilica of Sant'Apollinare Nuovo (early 6th century) has a procession of female martyrs walking toward the Virgin, their white garments set against a gold ground.

The Artists of Hagia Sophia (6th century CE)

The mosaics of Hagia Sophia in Constantinople, commissioned by Justinian I and dedicated in 537 CE, covered the dome, the apse, and the upper walls. The dome mosaic, which collapsed and was restored multiple times, depicted Christ Pantocrator. The apse mosaic of the Virgin and Child, dated to 867 CE, survives and is one of the most revered images in Eastern Orthodoxy. The tesserae are set at slightly varying angles to catch light from different directions, a technique that makes the surface shimmer as the viewer moves.

The Mosaicists of the Great Mosque of Damascus (715 CE)

The Umayyad caliph al-Walid I commissioned extensive mosaics for the Great Mosque of Damascus, completed in 715 CE. The mosaics depict landscapes, buildings, and trees in a style that blends Byzantine technique with Islamic aesthetic principles. The tesserae include glass and gold, and the work is attributed to Byzantine craftsmen sent by the emperor in Constantinople as a diplomatic gift. A 2021 study by Sara Fiorentino in Heritage examined Byzantine and Egyptian influences in Umayyad glass tesserae production, tracing supply chains and manufacturing techniques. Read the study at MDPI Heritage.

Antoni Gaudi (1852-1926)

Gaudi brought mosaic into modern architecture. His Park Guell in Barcelona (1900-1914) uses trencadis, a technique of breaking ceramic tiles and plates into irregular shards and setting them into mortar. The approach is a deliberate departure from the precise, regular tesserae of classical mosaic. Gaudi's mosaics cover benches, walls, and architectural surfaces with color that is exuberant and improvisational rather than controlled and systematic.

Dana Awartani (b. 1986)

At the 2026 Venice Biennale, Awartani filled the Saudi Arabian Pavilion with more than 29,000 hand-crafted clay bricks arranged in geometric, floral, and faunal motifs. The installation, May your tears never dry, you who weep over stones, draws on historic mosaic traditions from Palestine, Lebanon, and Syria. The bricks, made from four differently hued clay earths sourced from across Saudi Arabia, are assembled without binding agents. As the clay dries and cracks, the work becomes a physical manifestation of fragility and loss. Nearly 30,000 hours of artisanal labor went into its making, with artisans working alongside the artist in a collective practice rooted in craft traditions. Read more at designboom.

Jordan Nassar (b. 1985)

Nassar creates mosaics echoing Byzantine ruins, employing the ancient method of hand-cutting glass. In his 2025 exhibition REVELATION at James Cohan in New York, he reconstructed two archaeological antiquities, including a fragment of a mosaic floor from a 5th-6th century Byzantine structure. Nassar fills eroded areas with his own additions, including exotic animals and curving grape vines, raising questions about the symbolism of ruins and the narratives they can be used to construct. He describes "the act of remaking them as a tender gesture," reframing the historical lineage of the craft. Read more at James Cohan.

Contemporary Mosaic

Mosaic is not a dead technique. It is practiced and exhibited worldwide, with Ravenna serving as the living center of the art form. The Biennale di Mosaico Contemporaneo in Ravenna, the world's leading contemporary mosaic biennial, held its 9th edition in 2025-2026. The exhibition Beyond Mosaic Thinking in Ravenna opened on October 25, 2025, presenting work by 24 artists from different countries and illustrating the evolution of mosaic art and its ancient techniques interpreted in a modern key. Ravenna is internationally renowned for its Byzantine mosaic cycles and for the schools that continue to practice and teach the art of mosaic. Read more at Biennale di Mosaico Contemporaneo.

The Embassy of Italy in Panama presented MOSAICO. Italian Code of a Timeless Art, an immersive multimedia exhibition at Town Center Costa del Este in Panama City from June 13 to September 19, 2026. The exhibition takes visitors on a journey spanning more than 2,000 years, exploring images, symbols, techniques, and materials from Italy's most renowned mosaic sites: Rome, Pompeii, Aquileia, Ravenna, Palermo, Monreale, Piazza Armerina, and the submerged city of Baia. Read more at Embassy of Italy in Panama.

The Museum of Byzantine Culture in Thessaloniki opened a permanent open-air exhibition titled Ivy and Stone on June 16, 2026, presenting mosaic floors dating to the late fourth century CE from a luxurious residence in Thessaloniki. Throughout the summer, visitors can observe the conservation process of these mosaics as it unfolds and engage directly with conservators. Read more at Museum of Byzantine Culture.

How to Read a Mosaic

Start with the material. If the tesserae are stone, you are looking at a floor mosaic, probably Roman or Hellenistic. If they are glass, you are looking at a wall mosaic, probably Byzantine or later. Glass tesserae catch light in a way stone cannot. They reflect and refract, creating a surface that changes as you move. Stone tesserae absorb light, producing a matte, stable surface designed to be walked on.

Next, look at the size of the tesserae. The Alexander Mosaic uses cubes of about 0.5 centimeters, small enough to produce fine facial detail. Byzantine wall mosaics often use larger tesserae, 1 to 2 centimeters, because the images are viewed from a distance. The setting angle matters too. In the best Byzantine work, tesserae are not set flat. They are tilted slightly, each one angled to catch light from a specific direction. This is why the gold backgrounds in Ravenna and Hagia Sophia seem to move and shimmer.

Finally, look at the mortar. In Roman floor mosaics, the mortar is dense and hard, designed to bear weight. In Byzantine wall mosaics, the mortar is softer and the bedding layer is often left rough, creating a textured ground that adds depth to the surface. The 2025 Gerasa study confirmed that Roman mortars were of higher quality than later Byzantine and Umayyad mortars, with more careful selection of materials and tighter control over aggregate ratios.

Related Terms and Techniques

Mosaic overlaps with several other terms in this glossary. Fresco is the other great ancient and medieval architectural art form, but fresco is painted onto wet plaster while mosaic is built from solid pieces. Stained glass shares with mosaic the use of glass as a luminous architectural surface, but stained glass transmits light while mosaic reflects it. Byzantine art is the movement most associated with wall mosaic, and Roman art is the tradition that developed floor mosaic to its highest point. For more on how pattern and repetition function in visual art, read our post on texture in art.

See Mosaic in Person

Mosaic is best experienced in its architectural setting. A mosaic removed to a museum loses the light, the scale, and the spatial relationship that give it meaning. The buildings where mosaics live are the buildings where they were made.

Start at Ravenna, where eight early Christian and Byzantine buildings contain mosaics from the 5th and 6th centuries. San Vitale and the Mausoleum of Galla Placidia are the highlights. Then go to Istanbul for Hagia Sophia and the Chora Church, where the 14th-century mosaics represent a late Byzantine revival. For Roman floor mosaics, the National Archaeological Museum of Naples holds the Alexander Mosaic and the best collection from Pompeii. For modern mosaic, Park Guell in Barcelona shows what happens when the technique is freed from its architectural constraints and turned into pure color.

In 2026, contemporary mosaic can be seen at the Biennale di Mosaico Contemporaneo in Ravenna, the MOSAICO exhibition in Panama City (through September 19), and Ivy and Stone at the Museum of Byzantine Culture in Thessaloniki (open from June 16). Dana Awartani's brick mosaic installation is at the Saudi Arabian Pavilion at the Venice Biennale through November 22, 2026. For more on the broader context, read our entries on Byzantine art and fresco, or explore our post on mosaic art history and how to get started.