A few weeks ago I had tried online to book a tour of Gunkanjima (Battleship Island) but was disappointed to find that they were solidly booked out for all three days I was in Nagasaki. I went along to the docks anyway with my fingers crossed and was delighted to find that seats on the lower of the three decks on the boat were not sold online and there were plenty free.

Gunkanjima — its official name is Hashima — sits about 15km off the coast of Nagasaki, and its looming silhouette of crumbling concrete towers gives it the unmistakable look of a warship at anchor. Coal was discovered there in 1810, and after Mitsubishi took over in 1890 the island was progressively built up until it became, by 1959, the most densely populated place on earth, with over 5,000 people packed into just 6.3 hectares — a density nine times greater than central Tokyo. Every square metre was accounted for. Ordinary miners’ families made do with shared kitchens and narrow staircases, and the densely built-up residential areas left precious little room for privacy — couples seeking a quiet moment together had almost nowhere to go. Communication with the outside world was similarly constrained, with residents relying on just a handful of shared public telephones to keep in touch with family on the mainland. Because there was no ground-level space for children to play, a rooftop playground was built on top of one of the apartment blocks, and the island also had what is thought to be Japan’s first rooftop farm, where residents grew vegetables and taught children about agriculture.

For all its cramped conditions, life on Gunkanjima was in many ways surprisingly comfortable. Wages were high, rents low, and the island had a school, hospital, cinema, swimming pool and sports facilities. The miners’ relative prosperity showed up in a striking statistic: at a time when TV ownership across Japan stood at around 10%, every household on the island had one. The island was abandoned virtually overnight when the mine closed in 1974, and today it sits frozen in time — curtains still hanging in glassless windows, furniture left where it stood — a ghost town that was once, improbably, one of the most vibrant communities in Japan. It was designated a UNESCO World Heritage Site in 2015.

Nagasaki’s tram system, the Nagasaki Electric Tramway, has been running since 1915 and is one of the most charming ways to get around the city. Three colour-coded routes cover 11.5km of track, and the fare is a flat ¥150 (less than £1) regardless of distance or you can get a day pass for ¥600.