There are many broch sites in Orkney. These Iron Age structures date from about 600BC to perhaps 100AD, though some sites were occupied for longer, and typically comprise a large round tower, with hollow walls, which is often surrounded by a settlement. The brochs of Gurness and Midhowe face each other across Eynhallow Sound and are the best-preserved. Howe Broch near Stromness was dismantled in a destruction excavation, while Lingro Broch and settlement were destroyed by a misguided local farmer who should have known better.