Dublin, the capital of Ireland, was founded by the Vikings in the 9th century. Its English name comes from the Irish 'Dubh Linn,' meaning 'Black Pool,' while its official Irish name is 'Baile Átha Cliath' (Town of the Ford of the Reed Hurdles). Dublin is a UNESCO City of Literature, having produced four Nobel Prize winners in Literature: Yeats, Shaw, Beckett, and Heaney. The city is famous for the Book of Kells, an 8th-century illuminated manuscript kept at Trinity College. Dublin's geography is defined by the River Liffey, which divides the city into the Northside and the Southside. It is a major European tech hub, housing the European headquarters for giants like Google and Facebook in the 'Silicon Docks' area. One of the city's most visited sites is Phoenix Park, one of the largest walled city parks in Europe, which contains the official residence of the President of Ireland and a herd of wild fallow deer that have roamed there since the 17th century.