Opus signinum

Style of pavement first used in ancient Rome. It is marked by the use of a variety of materials, such as gravel, stone and earthenware, arranged in limestone or clay. The pattern would be extremely rough, or no pattern would exist at all. The trend began in the 1st century BC, proliferating in private homes as well as public buildings. By the 2nd century, opus signinum designs would give way to more patterned styles of pavement. The word derives from the town of Segni (Signa), near Rome where it was first used. Vitruvio (Roman Architect) describes creating and  applying  this style to make the covers of cisterns waterproof.