Lough Foyle

Lough Foyle is a broad tidal inlet between the Inishowen peninsula and the coast of Derry, opening northward to the Atlantic. The River Foyle enters its southern end and leads upstream to the walled city of Derry. During the siege of 1689 Jacobite forces stretched a boom across the river to prevent supplies reaching the city. Relief ships gathered in the lough and eventually broke through the barrier, bringing food to the besieged inhabitants. Control of the waterway had proved vital to the city's survival.