Wasserburg Zilly, Water castle in Osterwieck, Germany

Wasserburg Zilly is a water castle in Zilly, a district of Osterwieck, consisting of a partially preserved main castle and an outer bailey. The main castle and its rectangular bergfried, about 30 metres high with a baroque hood and 3.60-metre-thick walls, stand in the northeast; the outer bailey is partly preserved, and remains of the moats survive as a large pond. The whole complex measures 200 by 300 metres.

A castle called Xillingho is first recorded in 1172, linked to the deserted settlement of Zillingen. In 1251 the castle was held as a fief of the Counts of Regenstein and belonged to the Bishopric of Halberstadt. From 1272 Dittmar von Zillingen founded a local castle nobility, and in the 13th century a 32 × 30 m square keep was added as the main castle. In 1457 the castle was split, half as a fief to Heinrich von Stolberg and half to the Bishop of Halberstadt; from 1504 the bishop owned castle and village entirely and turned it into an administrative office.

The name Zilly comes from the abandoned settlement of Zillingen, where a castle called Xillingho was first recorded in 1172. The late-Renaissance "Bunte Stube" has large wall paintings and now serves as the wedding room; the 27 by 9 metre Rittersaal hosts exhibitions and events. The Förderverein Wasserburganlage Zilly runs guided tours.

The castle has belonged to the municipality of Zilly since 1990 and is looked after by the Förderverein der Wasserburganlage Zilly e. V., which runs guided tours. The grounds are partly preserved, with the main castle and the 30-metre bergfried intact, while the outer bailey survives only in part. The former moats remain as a large pond, and the 27 × 9 metre Rittersaal and the Bunte Stube can be seen on tours.

The rectangular keep in the north-east corner has walls 3.60 metres thick and, like the main castle, stands about 30 metres high under a baroque hood. The castle's total grounds measure 200 by 300 metres, and the former moats survive as a large pond.