Underneath, in an area larger than 10 football stadiums, will be a city with squares and cobbled streets, canals, shopping centres and golf courses.

The idea is to recreate summer, so that when the outside temperature is -30C, the residents of the Kazakh capital can play outdoor tennis, take boat rides or sip coffee on the pavement cafes.

Called Khan Shatyry, the project is designed by Lord Foster, who has recently built a giant glass pyramid in Astana.

"Nothing of the sort has been done before, and from the engineering point of view it's an extremely difficult project," says Fettah Tamince, the head of Turkey's development company Sembol that is building the tent.