Fort Hoofddijk was built in 1879 as one of the fortifications around Utrecht that formed part of the Nieuwe Hollandse Waterlinie, or 'New Dutch waterline'. This defense line made use of inundating parts of Holland to stop the advance of the enemy, but because Utrecht was on relatively high ground, it needed an additional ring of fortifications.
Today the Botanical Gardens of Utrecht University are located at the fortress site. It’s a beautiful place for a long walk along rare species of plants and flowers.References:
Krickenbeck moated castle is one of the oldest on the lower Rhine. Its history dates back to the year 1104, when the castle was first mentioned. It is unclear why the old castle, which was certainly inhabited by Count Reginar, was abandoned or destroyed. In the mid-13th century the castle was moved to the current location. At the end of the 14th century the new castle belonged to the Counts of Kleve.
Johann Friedrich II of Schesaberg converted the castle into a Baroque mansion between 1708-1721. On September 7, 1902, a fire destroyed the entire mansion. From 1903 to 1904, a three-winged castle was built in the Neo-Renaissance style. Today Krickenbeck is a conference center.