Oberburg und Unterburg Regensberg was designed as a fortified castle town and built by then modern contemporary criteria. The so-called Upper Castle (
Oberburg) comprises a rectangular plaza as main square which is surrounded two rows of houses, and into the limestone a deep water well was carved. The Lower Castle (
Unterburg) or lower town (
Unterstadt) was probably built in the 14th century nestled at the castle's hill outside of the town wall. Therefore, it was not involved in the modernization of the upper castle in 1689.
Rundturm The round tower (German:
Rundturm) is the only remnant of the mid-13th-century castle and is largely in its original state of construction. Atypical for the north-eastern Switzerland, it was built as a five-storey
keep made of local limestone, with a wall thickness of and a diameter of at its basement. The unique architectural design as round tower is presumably a reminiscence by
Lütold V to his wife noblewomen
Berta de Neuchâtel; in her native western Switzerland round towers then were disseminated. Originally, the tower had an elevated entrance and an high spire roof which was destroyed by lightning in 1766. The tower then received its present completion battlements and a new bridge that connected it with the palace. In 1894 the current single-storey entrance was built and thereafter the tower became a popular tourist destination as a belvedere. A thorough renovation of the tower was done in 2009, and in its interior also was established a small exhibition on the history of the castle and town.
Palas and economic buildings Situated in the north of the round tower, the palas also largely survived the devastating fire of 1540. In 1583 and 1585 it was replaced by
Vogt Vogel by a three-story building, which largely corresponds to the today's northern palace wing. The area was surrounded by the economic structures – wash house, stables, gardens, chapel – and separated with a wall and a gate leading into the
Oberstadt area. In 1883 a children's home has been set up in the former palas, and in 1890 the main building was widened and transformed into a school building which is now used by the
Stiftung Schloss Regensberg foundation. In the west new buildings were erected, and the
Unteres Haus building was converted into an accommodation building and a sheltered workshop. Prior the castle's gate and the stable barn were broken. == History ==