The correct answer is option 2, Yusuf Adil Shah. The Gol Gumbaz in Bijapur is known for its magnificent architecture, particularly its enormous dome, which is the second largest in the world. The monument was constructed during the reign of Yusuf Adil Shah, who was the Sultan of the Bijapur Sultanate. The Gol Gumbaz also houses a unique feature called the whispering gallery, where even the softest whispers can be heard clearly on the opposite side of the gallery due to its acoustic properties. Mahmud Gawan, mentioned in option 1, was a prominent minister during the Bahmani Sultanate, but he was not responsible for building the Gol Gumbaz. Ismail Adil Shah and Muhammad Adil Shah, mentioned in options 3 and 4 respectively, were also rulers of the Bijapur Sultanate, but they did not build the Gol Gumbaz.