The former Imperial Palace (Kaiserpfalz) in Kaiserslautern was built in around 1152 by Emperor Frederick I Barbarossa. The only remaining parts of the Imperial Palace are a few carved blocks of red sandstone and remnants of the stone outer wall of the double chapel added by Frederick II.
Following the excavation of the rest of the Imperial Palace and the evaluation of the findings, the city mounted the historic foundations. The Domus (imperial building) originally measured 25 by 19 meters and was 19 meters high. In order to get a real sense of the size of the building, a 3D steel and tamped concrete construction that imitates the size and shape of the Imperial Palace was built.
You can see the remains of the castle wall, which have now been fully uncovered, just next to what was the Imperial Palace. The Stapf fortress was also rebuilt in this location. The fortress was erected at the beginning of the Thirty Years’ War, in around 1619/1620, by fortress builder Adam Stapf on the orders of the widow of Frederick IV, Elector Palatine of the Rhine. Stapf built primary defensive walls with trenches, bastions and curtain walls which protected the medieval castle and city walls.
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.