Bergdorf Castle, located in Billelauf, is Hamburg's only preserved castle. Nowadays, it houses a museum. In around 1220, Count Albrecht von Orlamünde created a moated castle in the dammed Bille, which fell to the dukes of Saxe-Lauenburg in 1227. In 1420 Hamburg and Lübeck conquered the castle. It was the seat of the dual-city office of Bergedorf (city of Bergedorf, Vierlande and Geesthacht) and came under the sole ownership of Hamburg in 1867. Visible parts of the castle can be traced back to 1610 and 1661. In 1897-99 the north-east wing was renovated with a tower and entrance in the neo-Gothic style. The study, which was furnished in 1902 in the Vierländer style and with V&B wall tiles, was used by the Hamburg district of Bergedorf. Until 1927, divisions of the city council met in the castle, which was used after that for other official uses. Conservation and renovation work on the whole building from 1994 to 2002 was financed in part by large fund-raising campaigns by the public, and by friends of the house. The Museum for Bergedorf and the Vierlande is housed in the castle.