A burgus (Latin, plural burgi ) or turris ("tower")[1] is a small, tower-like fort of the Late Antiquity, which was sometimes protected by an outwork and surrounding ditches.
This entailed the construction of two-storey, rectangular towers (on average 8–12 m wide and 10–12 m high), so-called residual forts (German: Restkastelle) in limes camps that had already been largely denuded of their complements, and granaries (horrea) envisaged for border troops.
These burgi were essentially a development of the limes towers of the middle imperial period and consisted, in the case of the larger examples, of a tower-like central structure and outer fortifications (a rampart, defensive wall or palisade, surrounded by several ditches).
Buildings such as smaller watchtowers, fortlets (castella), civilian refuges at estates and fortified docks for riverboats, especially on the Upper Rhine and Danube, were also called burgi.
In the coastal cities of the Roman Empire and early Byzantium, local defensive complexes (burgi) were also built to protect important harbours.