Four sites were considered for the landings: Brittany, the Cotentin Peninsula, Normandy, and the Pas de Calais. As Brittany and Cotentin are peninsulas, it would have been possible for the Germans to cut off the Allied advance at a relatively narrow isthmus, so these sites were rejected. With the Pas de Calais being the closest point in continental Europe to Britain, the Germans considered it to be the most likely initial landing zone, so it was the most heavily fortified region. But it offered few opportunities for expansion, as the area is bounded by numerous rivers and canals, whereas landings on a broad front in Normandy would permit simultaneous threats against the port of Cherbourg, coastal ports further west in Brittany, and an overland attack towards Paris and eventually into Germany. Normandy was hence chosen as the landing site. The most serious drawback of the Normandy coast—the lack of port facilities—would be overcome through the development of artificial Mulberry harbours. A series of specialised tanks, nicknamed Hobart's Funnies, were created to deal with conditions expected during the Normandy Campaign, such as scaling sea walls and providing close support on the beach.