Golconda fort, near Hyderabad, is one of the most magnificient forts in India. it is famous for many engineering and architectural marvels. one of the marvel is the water supply system.but perhaps,more astonishing is the dome near the entrance to the fort. a hand-clap at a particular point under the dome reverberates and can be heard at the highest point of the fort, about a kilometre away . this was devised as a warning system. if a guard saw a suspicious movement outside the fort, he clapped at the particular point under the dome, and the army inside the fort was alerted to the danger of the approaching army