Future Cities: Singapore focuses on the exceptionally forward-looking urban approach of the island nation to learn about the challenges of planning for future generations.

(CNN) They're found 150 meters below the ground, taller than a nine-storey building and, once complete, will store 9 million barrels of oil.

The Jurong rock caverns in Singapore are defying the challenge of limited land space by creating a deep underground storage facility for the city-state's oil reserves.

This is the first project of its kind in South-East Asia, but it has been tried before to great success elsewhere in the world.

"In Norway they use it for water treatment plans, in South Korea and Japan they use it for oil storage," says David Tan, Assistant Chief Executive Officer of the Technical & Professional Services Group at JTC Corporation who are handling the industrial development in Singapore.

After eight years in development, the first cavern opened in 2014, with four more in the pipeline.

Read More