Snowdonia has many historic sites, including Stone Age burial chambers, Iron age hill forts, Roman forts, churches, and medieval castles. There are also industrial sites including large slate quarries, copper mines, and woolen mills. More than 26,000 people live in Snowdonia. The area attracts over six million visitors every year. Most of the land is either open or mountainous land, but there is also some farm-land. Snowdonia National Park does not include the town of Blaenau Ffestiniog, which is like an island in the centre of the park.