Mausoleum, Neoclassical ducal mausoleum in Gertrudenfriedhof, Oldenburg, Germany

The Mausoleum is a neoclassical building in Oldenburg with a square floor plan, a flat gable roof, and a raised stone platform. The corners of the platform feature decorative false stone blocks, and the interior holds several wall recesses designed to serve as burial chambers.

A duke commissioned the building between 1786 and 1790 after his wife died in childbirth. It was the first neoclassical structure in the city and had a lasting influence on local architecture in the decades that followed.

The mausoleum holds the remains of Duke Peter I and his wife Friederike, who died in 1785 giving birth to their third child; her body was moved here from the chapel of Eutin Castle in 1790. The marble monument to the couple, carved by Stuttgart sculptor Johann Heinrich Dannecker, bears the inscription "Vater dem Lande zu seyn, war ihm höchster Beruf" (to be a father to the land was his highest calling). The central sandstone-framed niche in the north wall is dedicated to Friederike's memory.

The mausoleum sits at the northeastern edge of the Gertrudenfriedhof, Oldenburg's main cemetery outside the old town. The building is normally closed to the public; it opened for interior visits only in November 2013, after the 2012/2013 restoration. Access to the crypt stair, moved to its present spot in 1895, is not part of regular visits.

The restoration took place in 2012/2013, and in November 2013 the building was opened to the public for the first time, although it is normally closed. The crypt entrance lay directly beneath the glass dome until 1895, when it was moved to its present position. The dome weighs about one tonne and is glazed with very thin etched glass.