From its towering "supertree" vertical gardens to a Formula 1 night race, Singapore is known for many attractions; underground space is not one of them.
But that may soon change, as the city-state prepares to unveil an Underground Master Plan in 2019.
With some 5.6 million people in an area three-fifths the size of New York City — and with the population estimated to grow to 6.9 million by 2030 — the island nation is fast running out of space.