The 17th century monument of Bijapur, Gol Gumbaz is the mausoleum of Muhammad Adil Shah. It is said to be an astonishing feat of engineering with its enormous 'Whispering dome', which is second largest in the world, second only to St. Peter's Basilica in Rome and is 124 feet in diameter. This huge dome is not supported by pillar and is so built that even the faintest whisper or ruffle of a paper echoes throughout the dome, can be heard across a distance of 37 m and returns to the listener nine times. The gallery around the dome offers some fantastic views of the city. The unique architectural style of the building includes the four minarets surrounding it. Comparable to the mausoleum of the father of Adil Shah known as Ibrahim Rauza, it is one of the biggest single chamber structures in the world.