After an expansion during the reign of the Umayyad caliph al-Walid I, it now incorporates the final resting place of Muhammad and the first two Rashidun caliphs Abu Bakr and Umar. One of the most notable features of the site is the Green Dome in the south-east corner of the mosque, originally Aisha's house, where the tomb of Muhammad is located. In 1279, a wooden cupola was built over the tomb which was later rebuilt and renovated multiple times in late 15th century and once in 1817. The current dome was added in 1818 by the Ottoman sultan Mahmud II, and it was first painted green in 1837, hence becoming known as the "Green Dome".