Shiryōkaku (四稜郭) (literally, 'four-point fort') is a fort in the city of Hakodate. It was constructed in April 1869, during the Battle of Hakodate, three kilometres to the northeast of Goryōkaku by two hundred soldiers of the former Tokugawa shogunate and a hundred local villagers, likely under the direction of Ōtori Keisuke.
The fort covers an area of 21,500 m2, stretching approximately a hundred metres east to west and seventy metres north to south; the earthworks rise to a height of 3 m with a width of 5.4 m; they are surrounded by a dry moat 0.9 m deep and 2.7 m wide; the entrance is to the southwest.
Shiryōkaku fell to government forces within a few hours on 11 May 1869.
In 1934 the area was designated an Historic Site. Repairs were carried out from 1970-2 and again in 1990.
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.