Called Astana, it is the world’s latest example of a rare but persistent type, the capital built from zero. It is in a line that includes St Petersburg, Washington DC, Canberra, Ankara and Brasilia and like them it provokes a question: can a city, in all its teeming complexity, really be planned? Or does the attempt lead only to a synthetic simulacrum, a kind-of city that is not quite the real thing?