As if from a dream, the island floated over the sea like a terra-cotta dreadnought from a century ago. I'd arrived at Gunkanjima, or Battleship Island, and its profile was unmistakable from the deck of my ferry battling high waves and winds.

Formally known as Hashima Island, Gunkanjima is Japan's greatest ruin of modern times. Once home to thousands, the mining colony was abandoned 40 years ago and is now a place of rust, rubble and ghosts.

Recent years have seen an explosion in travel to Japan's abandoned buildings, theme parks and industrial sites. This boom in haikyo (ruins) tourism, while a niche phenomenon that can sometimes involve illegal trespass, is set to expand with this year's addition of Gunkanjima to the UNESCO World Heritage list. Opened to visitors in 2009, the island mine is a 30-minute boat ride from Nagasaki City.