The open, shady square outside Lamu Fort near the island's administrative offices is used as a meeting point during the heat of the day. Lamu Fort is one of the most imposing historic structures in Kenya, only exceeded in size by Fort Jesus in Mombasa. Construction of its massive walls began in 1813, shortly after Lamu's victory over Pate and Mombasa in the battle of Shela. The fort took eight years to complete under the supervision of Omani Arabs.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.