The underground Basilica Cistern (Turkish: Yerebatan Sarayı - "Sunken Palace", or Yerebatan Sarnıcı - "Sunken Cistern"), is the largest of several hundred ancient cisterns that store water beneath the city of Istanbul. The cistern was built in the 6th century during the reign of Byzantine Emperor Justinian I, and is located 500 feet (150 m) southwest of the Hagia Sophia on the historical peninsula of Sarayburnu, . [Wikipedia]

Above is the "teardrop" column.