St. Nicholas Church on the Old Market Square is the dominant landmark of Potsdam's city centre — a neoclassical church with a massive copper dome designed by Karl Friedrich Schinkel and completed in 1850. The scale is deliberately monumental; Frederick William IV wanted a church that would anchor the square as firmly as a Roman pantheon anchors a Roman piazza. The result is one of the finest examples of neoclassical religious architecture in Germany.
The interior is spacious, light-filled, and relatively austere — columns, a coffered ceiling, and a central dome letting in natural light from high windows. The church was badly damaged in the 1945 bombing and stood semi-ruined through much of the East German period, with full restoration completed only in the 1990s. It sits directly opposite the reconstructed City Palace (now the Brandenburg state parliament) on the Old Market Square, forming an ensemble that gives Potsdam a genuinely impressive civic heart.