Fujairah is the only one of the Emirates with a coastline solely on the Gulf of Oman. Its importance in antiquity was its location at the mouth of Wadi Ham, a crucial trade route from the Omani coast through the high Al Hajar mountains to the Persian Gulf coast. Archaeological evidence reveals human occupation for as much as 4,000 years. The Portuguese fortress at Badiyah was constructed of stones from a 3rd Century BCE watchtower. Prior to the formation of the emirates, the community traded in pearls and dates from its extensive palm groves. There are also numerous Islamic-era fortresses in the region, including the photogenic Fujairah Fortress. The Al Badiyah Mosque, constructed of mud and bricks with an unusual four domes and no minaret, is the oldest still in use in the Emirates, dating from 1446.