The Burcht van Leiden is an old shell keep in Leiden constructed in the 11th century. It is located at the spot where two tributaries of the Rhine come together, the Leidse Rijn, and another river, now a canal. The structure is on top of a motte, and is today a public park.
From humble beginnings, the hill was raised during various periods of history up to 9 meters above the surrounding landscape in the 11th century. Ada van Holland used the keep as a residence until her father died in 1203 and she was captured by her uncle. In the same year the previous stone building was rebuilt after an attack on the castle, with tuff stone, and after Ada's removal, in 1204 it was attacked again and rebuilt with brick.
Later in the 13th century the building was considered antiquated, since more and more townspeople and houses were built around the base of the hill, making defenses impossible without destroying most of the city. The old 'interior keep' that had been built against the interior walls (a similar ronded keep construction can still be seen in Teylingen) was slowly dismantled and reused for city construction.
As the city of Leiden grew around it in the 13th and 14th centuries, the ruined castle lost its military function. The location became a romantic patriotic symbol after the Siege of Leiden in 1574. In 1651 the city bought the premises to make it into a water tower for public use. A system of waterpipes leading to squares in the city is still intact. In this period a new portal on the keep wall was designed in 1662 with heraldric symbols by Rombout Verhulst, denoting the leading families of the city. There are two other gates to the Burcht, one at the base of the hill with wrought iron heraldric weapons, built in 1653, and one on the south side of the complex, which itself forms a gateway to the park.
References:The Broch of Clickimin is a large and well preserved, though somewhat restored broch near Lerwick. Originally built on an island in Clickimin Loch (now increased in size by silting and drainage), it was approached by a stone causeway. The water-level in the loch was reduced in 1874, leaving the broch high and dry. The broch is situated within a walled enclosure and, unusually for brochs, features a large 'blockhouse' between the opening in the enclosure and the broch itself. Another unusual feature is a stone slab featuring sculptured footprints, located in the causeway which approached the site. Situated across the loch is the Clickimin Leisure Centre.