The limestone cave complex at Dunmore stretches around 0.5 km (0.25 miles) underground and descends to a depth of 46 m (150 ft). It is open for guided tours of the caverns, which are rich in gleaming limestone stalactites and stalagmites that have been forming, drip by drip, for more than 300 million years. The most spectacular is a vast, colonnaded pillar dubbed the ‘Market Cross’, which is found in a chamber known as the ‘Town Hall’ and is over five m (16.5 ft) high. There is evidence in ancient Irish literature of man settling in the caves as far back as the ninth century, while bones and teeth found in the inner chambers of the complex are thought to be the remains of Vikings murdered in 928. In addition, a hoard of silver and bronze coins, wire buttons and ingots were discovered there in 1999; they are currently displayed in the National Museum of Ireland in Dublin and are believed to date from around 970 AD. A small visitor center showcases the history and geology of the cave complex.