Klopp Castle is one of the oldest castles in the Middle Rhenish region, but most of its medieval buildings no longer exist. First mentioned in 1105, the castle served as the residence for the men of the archbishop of Mainz and, from 15th century, for a Mainz canon who was in charge of the administration of the Cathedral chapter.
Today, 19th-century architecture dominates the shape of the building: In 1853, Ludwig Maria Cron rebuilt parts of it (the bridge, the gatehouse, the battlements, and the upper border of the keep). From 1875 to 1879, a neo-Gothic main building resembling a great hall was constructed based on plans by the architect and Mayor Eberhard Soherr. From 1897, it has housed the town council offices.
The lower part of the Roman keep, parts of the southern ring wall with remnants of the battlements, and the moat are still preserved from the 13th century.