 In 1900 , near the site of the ancient Byzantine city of Theodosia , thirteen large piles of stones were discovered by Zibold who was a forester and engineer in charge of this area . Each stone pile covered just over 900 square metres ( 9 @,@ 700 sq ft ) and was about 10 metres ( 33 ft ) tall . The finds were associated with the remains of 75 @-@ millimetre diameter ( 3 @.@ 0 in ) terracotta pipes that apparently led to wells and fountains in the city . Zibold concluded that the stacks of stone were condensers that supplied Theodosia with water ; and calculated that each air well produced more than 55 @,@ 400 litres ( 12 @,@ 200 imp gal ; 14 @,@ 600 US gal ) each day . 
