Few places evoke the rise and fall of Japan's industrial might than the head office of the Imperial Steel Works in Kitakyushu. The red brick Meiji Era building was the heart of the nation's first big steelworks. Now it's a UNESCO World Heritage site.

Kitakyushu, with nearly a million people, embodies the struggle of Japan's cities to adapt to a future where citizens are older, workers are fewer and many houses are emptying. The emblems of government efforts to revitalize the economy — a billion-dollar airport, a robotics factory — stand beside the empty lots, an idle blast furnace and shuttered shops.

Five hours west of Tokyo by shinkansen, Kitakyushu lost over 15,000 people in the five years to 2015, more than any other city in the country apart from those evacuated because of the Fukushima nuclear disaster. More than 100,000 residents have gone since the peak in 1979, and half of the factory jobs have disappeared with them.