A Burh is a defended settlement dating to the Anglo-Saxon period, built to defend against the Viking invasion. Small ones were little more than forts but larger ones would have their own judicial administration and an established market as well as a military presence. Many towns with names that have 'borough', 'burgh' or 'bury' originate from saxon burhs. The picture shows a plan of a late saxon burh at Eashing in Surrey. The fortifications often included revetted embankments (ie: embankments supported by stones, timber, etc.)
A Burh is an Anglo-Saxon name for a fortified town or other defended site, such as a hill fort. The boundaries of ancient burhs can often still be traced to modern urban borough limits. A 10th century document called the Burghal Hidage cites 33 burhs in Wessex, built to defend the region against Viking raids.