Mosaic is an art form that uses small pieces of colored stone and glass, called tessera (plural:tesserae), to create designs or pictures set in cement. In antiquity, mosaics were created exclusively to decorate architectural surfaces such as floors, walls, and vaults, and examples have been found in a wide variety of contexts, including palaces, houses, baths, mausoleums, synagogues, and churches. Some scholars have argued that the designs in mosaic floors were inspired by those in carpets, while others have suggestedthat they mimicked painted, wooden, or stucco relief ceiling decorations.

In Book 7 of his Ten Books on Architecture, the Roman architect Vitruvius (ca. 80–70 to after 15 BCE) described several methods for preparing the foundation of a mosaic floor.

Typically, a pounded-gravel base was prepared to receive concrete or lime mortar in ascending layers of fineness. Once the base was prepared and the concrete or mortar was in place, the actual setting of the design could begin, following one of three methods of mosaic construction—the direct method, the indirect method, and the reverse method—although any combination of these could be used on a floor.

The direct method involved setting the individual tesserae directly in wet cement. The indirect method involved setting the tesserae in sand and gluing a cloth to their upper surface. Once the glue had set, the complete mosaic was lifted from the sand and set into wet cement. When the cement was dry the glue would
be dissolved with hot water to reveal the design. The reverse method was a variation of the indirect method; here, instead of the final surface of the tesserae being laid face-up, the pieces were glued face-down onto a cartoon (a preliminary full-scale sketch) drawn or painted on cloth. Mosaics were a popular art form for thousands of years.

While the earliest manifestations of mosaic work can be found in Sumerian architecture of the third millennium BCE, the first true mosaic floors were unearthed during excavations in Olynthus, an ancient city in northern Greece, and in the ancient Macedonian capital of Pella. Others have been found on the islands of Delos and Rhodes and from Pergamum in Asia Minor (Turkey). The earliest Greek mosaics depicted mythological subjects and were made with colored pebbles, but by the third century BCE, colored stones and glass were introduced.Mosaic floors became widespread during Roman times. following the earlier Greek examples, Roman mosaics usually had a large central square (emblemata) depicting a mythological or figurative scene and surrounded by a decorative border of floral and geometric motifs. The emblemata was a portable mosaic panel that would have been made elsewhere and inserted into a pavement while the rest of the mosaic was laid on the spot. While the earliest Roman mosaics continued the late Hellenistic tradition of brilliant color, they were eventually replaced by the black-and-white mosaics that came to characterize the mosaic pavements of Italy.

As Rome expanded its boundaries from the first century BCE to the first and early second centuries CE, the practice of mosaic making spread throughout western Europe and the ancient Mediterranean region, extending to Spain, Gaul (france), Britain, Germany, North Africa, and as far east as Syria. As the art form spread, moreover, each geographic region developed its own regional style and repertoire. The mosaic floors of Roman Syria (figure 1), for example, are characterized by lush colors, mythological or figurative scenes set in large central squares and surrounded by elaborate borders, inscriptions to help identify the scenes or figures
portrayed, and illusionistic motifs inspired by architectural details.

Ancient mosaic artists probably worked in workshops where there was a clear division of labor between the principal artist who designed the mosaic floor and the supporting craftsmen and apprentices who did the routine work of laying the background.

The size of these workshops clearly varied from place to place, from one or two craftsmen to as many as a dozen during periods of high demand and productivity. Indeed, the continued existence of any workshop depended on the steady supply of mosaic commissions, and there is even some evidence of itinerant mosaic artists moving from one province to another to secure work.

Each workshop typically developed a range of compositions and trademark details that became its stock in trade.

In Roman Britain, for example, scholars have identified at least six separate workshops or schools, each with its own unique compositional arrangements and schemes. Most mosaic artists probably drew on a combination of training, imagination, and their memory of other mosaic floors they had seen to create their own unique compositions and designs. While some scholars have argued that pattern books (collections of designs, patterns, and motifs) were used to transmit compositions and decorative elements from one region to the next, none have survived from antiquity to support this theory.

In addition to a stock repertoire of figurative compositions and elements, the ancient mosaic artist had access to hundreds of ornamental patterns and geometric designs that were based on the standard ornamental vocabulary of Greek art. Designs ranged from very simple arrangements of geometric patterns
to immensely complicated and complex combinations (figure 2). Some of the most popular geometric designs in Roman times were the meander (a labyrinth-like design), the guilloche (a braid design), and the lozenge (a diamond-shaped motif), to name only a few. In recent years scholars have identified more than 1,600 patterns and designs that were used in mosaic pavements between the first century BCE and the sixth century CE.

Within the typical Roman house there would have been a clear prioritization of spaces.

The most elaborate and expensive mosaic floors, for example, would have been reserved for the oecus (parlor or reception room) and triclinium (dining room), while less elaborate mosaics would have been used in bedrooms and bath suites. By contrast, the simplest and least costly mosaic floors would have been set in less prominent spaces, such as hallways, walkways, and support spaces. In general, figurative scenes tended to be reserved for spaces that imposed a particular viewpoint, such as the oecus and triclinium, while floral and geometric patterns were used for spaces that moved the eye forward but did not need to be viewed from a specific viewpoint. Similarly, a relationship can often be found between the themes of floor designs and the function of the spaces they were intended to decorate.

In oeci, for example, the owner might select a theme from mythology, literature, or daily life, while triclinia often featured drinking and banquet scenes, or general subjects from myth and legend. Bath suites often depicted
themes associated with water and exercise, such as dolphins, fish, sea nymphs (female spirits), or athletes, while bedrooms might feature mosaic floors depicting Venus and Cupid (the Roman gods of love) or amorous encounters between satyrs (half-bestial woodland spirits) and bacchantes (female devotees of Bacchus, the Roman god of wine and revelry). Mausoleums often featured representations of an eschatological nature, while mosaics in churches and synagogues held religious imagery.