Burgruine Henneberg, Castle ruin in Poppenbüttel, Germany

Burgruine Henneberg is a 1:4-scale replica of the Thuringian castle of the same name, built as an artificial ruin on a 15-metre mound raised over three years of labour. A 12-metre tower of light grey rough-hewn stone with a dark conical roof and a row of narrow windows rises beside a lower ruined wall with a pointed arch. Inside are a 23 m² Rittersaal with a 20 m² gallery, a 7 m² chamber and a spiral stair to the tower; cracks were faked in the masonry for an antique look.

Albert Caesar Henneberg bought a former clay pit by the Poppenbütteler Schleuse in 1875, had a 15-metre hill raised over three years and built the 1:4 replica of Burg Henneberg from 1884 to 1887 to plans by August Pieper. Until 1907 it housed the family archive, also used by Braunschweig historians. After 1930 a Liedertafel rehearsed here; in 1942 the building passed to Hamburg, and in 1988 it faced demolition before a private buyer restored it in 1990.

The name Alsterschlösschen refers to the small castle by the Alster. The building was a folly, a 1:4 replica of the Thuringian seat of the Counts of Henneberg, chosen because of the shared family name, although no kinship existed. From 2014 the non-profit Stiftung Burg Henneberg has used it for cultural purposes, and since 2021 commercial use has also been permitted.

The artificial hill was raised over three years of labour, and the tower rises 12 metres above it; a spiral staircase inside leads up, while an open stairway runs around the outside of the building. The structure stands by the Poppenbütteler Schleuse in Park Marienhof, whose 3.5 hectares slope gently toward the Alster. The site was opened to the public only after 2014, when use passed to the non-profit Stiftung Burg Henneberg.

The tower's masonry holds cracks that were carved in deliberately, to give the new building an aged look. The hill beneath it is artificial too: a rocky 15-metre mound heaped up over three years of labour before construction began.