The Citadel of Calais was built between 1560 and 1571 on the site of a former medieval castle which was built in 1229 by Philippe de Hureprel. Its purpose of its construction was to fend off would-be invaders, but it wasn't long until the city was successfully invaded by Archduke Albert of Austria on 24 April 1596. Both Louis XIII and Cardinal Richelieu at one time considered expanding the citadel and Calais into a great walled city for military harbour purposes but the proposals came to nothing.
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.