texts suggest that the tears on the column pay tribute to the hundreds of slaves who died during the construction of the Basilica Cistern. The majority of the columns in the cistern appear to have been recycled from the ruins of older buildings (a process called 'spoliation'), likely brought to Constantinople from various parts of the empire, together with those that were used in the construction of Hagia Sophia. They are carved out of different types of marble and granite. Fifty-two stone steps descend into the cistern which is surrounded by a firebrick wall with a thickness of and coated with a waterproofing mortar. The Basilica Cistern's water came from the Eğrikapı Water Distribution Centre in the Belgrade Forest, which lie north of the city. It traveled via the Valens (Bozdoğan) Aqueduct, and the original Mağlova Aqueduct, which was built by the Emperor Justinian. The weight of the cistern is carried on the columns by means of the cross-shaped vaults and round arches of its roof. The Basilica Cistern has been restored several times since its original creation. The first repairs were carried out in the 18th century during the reign of the Ottoman sultan Ahmed III in 1723 by the architect Muhammad Ağa of Kayseri. The second major repair was completed during the 19th century reign of Sultan Abdulhamid II (1876–1909). Cracks in the masonry and damaged columns were repaired in 1968, with additional restoration in 1985 by the Istanbul Metropolitan Museum. During the 1985 restoration, 50,000 tons of mud were removed from the cistern, and platforms were erected to replace the boats previously used for touring the cistern. The cistern was opened to the public on 9 September 1987. It underwent additional cleaning In May 1994. Then in 2017 it was once again closed for restoration and earthquake-proofing, reopening to the public in 2022. Medusa column bases The bases of two columns In the northwest corner of the cistern reuse blocks carved with the face of Medusa. The origin of the two heads is unknown, though it is thought that they were brought to the cistern after being removed from a building of the late Roman period. There is no evidence to suggest that they were previously used as column bases. Tradition has it that the blocks are oriented sideways and inverted in order to negate the power of the Gorgons' gaze; but it is more likely that