Opus tessellatum floor mosaic, depicting Triton, inside the women's changing-room of the Thermae, archeological site of Herculaneum, Pompeii, province of Naples, Campania region, southern Italy, Europe
Palazzo Massimo alle Terme in Rome | Opus vermiculatum is a method of laying mosaic tesserae to emphasise an outline around a subject. This can be of one or more rows and may also provide background contrast, eg as a shadow, sometimes with Opus tessellatum. The outline created is often light and offset by a dark background for greater contrast. The name opus vermiculatum literally means "worm-like work", and has been described as one of the most demanding and elaborate forms of mosaic work.