The ruined Qutb Shahi fortress on a granite outcrop 11km west of the Old City, once the diamond-trading capital of the medieval world — the Koh-i-Noor came from here. The acoustic trick at the main gate is famous: a single handclap carries all the way to the summit pavilion 100 metres above, a feat of Qutb Shahi engineering that served as a warning system. Climb the ramparts for wide views over the Deccan plateau. In the evenings a sound and light show runs in English and Telugu, narrating the fort's history against the illuminated stonework.