Bukhara is the one Silk Road city that came through the centuries more or less whole: two hundred monuments inside a maze of mud-brick lanes, the domes of the covered bazaars rising between the rooftops. Everything centres on the Poi Kalon, where a brick minaret from 1127 has stood for nine hundred years — Genghis Khan, the story goes, left it alone out of sheer astonishment. Around it lie madrasas, water cisterns and the caravanserais where silk and lapis changed hands.