Casteldoria Castle was built around the 12th century by the Genoese Doria family, and passed from the Genoese dominion to the Aragonese, then to the Arborea Giudicato and lastly to the Malaspina family.
Only a few ruins remain of the fortress: parts of the walls, the remains of a chapel and a large cistern that was probably used to collect and store water. The famous tower, on the other hand, is well-preserved, and is an important part of the castle, built in large, rectangular granite blocks set in mortar. Twenty metres high, it has a pentagonal layout with the entrance on the north-eastern side. On the same side are two large, non-aligned openings, and a large window on the opposite side on the first floor. Inside, the castle has three wooden floors with a tiled roof and walkway. The last floor was created from what was originally a mezzanine floor before a terrace.
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.