The Walls of Thessaloniki are the city walls surrounding the city during the Middle Ages and until the late 19th century. Large parts of the walls, including the entire seaward section, were demolished as part of the Ottoman authorities' restructuring of Thessaloniki's urban fabric. The city was fortified from its establishment in the late 4th century BC, but the present walls date from the early Byzantine period, ca. 390, and incorporate parts of an earlier, late 3rd-century wall. The walls consist of the typical late Roman mixed construction of ashlar masonry alternating with bands of brick. The northern part of the walls adjoins the acropolis of the city, which formed a separate fortified enceinte, and within it lies another citadel, the Heptapyrgion (Seven Towers), popularly known by the Ottoman translation of the name, Yedi Kule.
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.