Dublin is the capital city of Ireland, and is home to a population of 1.2 million people within its greater metropolitan area. It is located on the east coast, with a harbour opening to the Irish Sea which separates Ireland from Britain. About half the population of Dublin is under the age of 25, so it is one of Europe's youngest capital cities. The city is bisected from east to west by the River Liffey, which separates the homely north side from the more cosmopolitan and trendy south side. The city is serviced by public bus transportation (Dublin Bus) and by light rail (Dublin Area Rapid Transport), the latter of which hugs the coastline and circles the harbour.
Early settlements around what is now Dublin began their transformation into a city with the arrival of a Viking fleet in 837 AD. These Vikings were impressed with the area, and several years later constructed a fortress which they called by the Irish name Dubh Linn, which means 'black pool'. The city expanded slowly in the medieval period, but experienced huge growth in the eighteenth century. Much of the splendid architecture of the city dates from this 'Georgian' period.
Today Dublin is a rapidly-growing city, which boasts a strong presence of IT and other growth-oriented industry. With the help of the young population and strong tourism, the nightlife is lively every night of the week. Two of Europe's top institutions of higher education, Trinity College Dublin and University College Dublin, are located here. The city is also home to a particularly strong cultural sector, including theatre, sport, music, art and film.