Ruinenberg, Artificial ruins garden on Sanssouci Park hill, Potsdam, Germany.

Ruinenberg is a hilltop ensemble of sham antique ruins built around a circular water basin 37.66 metres across and 3.77 metres deep. On the south side stand a 16-column Doric monopteros with a dome damaged on one side, three tall Ionic columns carrying an entablature, and a broken column leaning against them; a small fieldstone pyramid and a wall modelled on a Roman theatre surround the pool. The Norman Tower, a 23-metre lookout, was added in 1846.

Frederick the Great had a circular basin 37.66 m across and 3.77 m deep built on the hilltop in 1748 to feed the Sanssouci fountains, but the windmill pumps never delivered enough water and he abandoned the project in 1780 after spending 168,490 talers. Around the basin Knobelsdorff and the theatre painter Innocente Bellavite placed a 16-column Monopteros, three Ionic columns, a broken column and a pyramid. Frederick William IV had Lenné lay out the surrounding garden from 1841, and 50,000 trees and shrubs were planted by November 1842.

The ruins were stage sets, not remains: theatre painter Innocente Bellavite worked with Knobelsdorff on the mock-antique pieces, and the broken column beside the three Ionic ones was placed to look as if it had toppled and caught itself by chance. Frederick William IV later had Lenné plant 50,000 trees and shrubs here by November 1842.

The hilltop is reachable on foot via several pathways that climb from different parts of the park, some quite steep. Comfortable shoes are important since the ascent can be tiring and some areas are uneven.

The round basin on the summit measures 37.66 metres across and is 3.77 metres deep, holding roughly 4,200 cubic metres. Frederick the Great saw a fountain play below the picture gallery only once, on Good Friday 1754, after a wet winter had filled the basin. The whole failed project had cost 168,490 thalers by the time he abandoned it in 1780.