In the 11th century a stone keep (Gravensteen Castle, restored) was built on the south-west of Oudburg Island. As described in written sources, this 'domus lapidea' was rectangular (ca. 13.5 x 31 m); it is partially preserved in the present castle, which essentially dates from ca. 1180 (built by count Philip of Alsace). The presence of this building fostered trade and house construction along the banks of the Leie. The city's oldest market, the Vismarkt (now the Groentemarkt), was built near by. It was abandoned in the 14th century; in 1885 the city of Ghent bought the castle and renovated it.