A man rides a donkey and a young boy bicycles along the waterfront of Lamu town; this is the island's widest road. In the absence of vehicles, which are banned in the island, donkeys are the principal means of transport and carrying heavy loads.Situated 150 miles north-northeast of Mombasa, Lamu town dates from the 15th century AD. The island's importance lies in the fact that it has the only certain source of sweet groundwater in the entire district. The town was declared a World Heritage Site by UNESCO in 2001 because it is the oldest and best preserved Swahili settlement in East Africa. Moreover, its architecture and urban development graphically demonstrates the diverse cultural influences that came together over many centuries to produce a distinctively local Swahili style and culture.Most of the storied buildings are built of coral and lime. The sea wall was built by prisoners of war during the First World War.