Blocks

Concrete blocks forming one of the 'Churchill Barriers' in Orkney.
The Churchill Barriers are four causeways in the Orkney Islands with a total length of 2.3 kilometres (1.4 mi). They link the Orkney Mainland in the north to the island of South Ronaldsay via Burray and two smaller islands.
The barriers were built between May 1940 and September 1944, primarily as naval defences to protect the anchorage at Scapa Flow but since 12 May 1945, serve as road links between the islands.