Temperature is also a factor in Helsinki, Finland, where authorities have built nine million cubic metres of facilities under the city – including shops, a running track, ice-hockey rink and swimming pool.
Lead designer of the city’s underground master plan, Eija Kivilaakso, says conditions underground are often more favourable than those above, especially in winter, when surface temperatures can drop below -20C.
“With the weather in Helsinki, it’s nice to work or get coffee underground – we don’t have to go out in the rain or the cold.”