With surface space at a premium, global cities go underground

Cities from Helsinki to Singapore are exploring the benefits of expanding towards the centre of the earth.

Crowds, weather, expensive real estate and vulnerability to climate change are prompting urban planners to turn their eye to the potential of usable spaces below street level.

From an underground park in a forgotten century-old tram terminal in Manhattan to Mexico City's inverted 300 metre underground pyramid - called the Earthscraper - architects are reimagining spaces for people and not just infrastructure in cities of the future.

"There are real opportunities to develop underground to accommodate density for cities that are already overcrowded or growing," said Clara Irazabal, assistant professor at the graduate school of architecture, planning and preservation at Columbia University, New York. "It can expand efficiency, reduce commuting times and improve quality of life."

Singapore is planning a 20 hectare subterranean labyrinth that could house as many as 4,200 scientists and researchers in soundproof labs and data centres carved out of caves, according to JTC, a property developer that commissioned a feasibility study on the project.

The city state opened the first underground oil-storage facility in Southeast Asia this month, freeing space three times the size of New York's Grand Central Station for chemical manufacturing above ground. The project caps a 30-year effort to create a petrochemical hub. It began when officials merged seven offshore islets and then spent US$749 million to dig rock caverns that can hold enough liquid hydrocarbon to fill 600 Olympic-sized swimming pools.