Douglas has been the capital, principal port, and ferry terminal of the island since 1869, the island itself having become a Crown possession in 1828. It gets its name from the Dhoo and Glass Rivers. Douglas, which developed around smuggling, now has light industry, tourism, the seat of the island's parliament, the Tynwald and House of Keys (oldest parliament in the world). Douglas boasts Castle Mona (1804), and the Tower of Refuge (1832), as well as the impressive Manx Electric Railway (1893) and Douglas horse-drawn trams (1876), both of which are still in service. Located along the Irish Sea, the Isle of Man and its wooded hills and jagged coastline offer some of the country’s most spectacular scenery. The island was once occupied by Celts who left behind Iron Age forts and huts. Though Romans never settled here, it is believed Celtic Christianity was introduced by St. Patrick and flourished from the fifth century to eighth century when Vikings conquered the island. On the island visit the Calf of Man bird sanctuary, and Castle Rushen at Castletown, the former capital.