During the War of Power, two huge sa'angreal, one attuned to saidin and one to saidar, were constructed. The Choedan Kal were to be used to destroy the Shadow's forces and erect a barrier around Shayol Ghul until there was a safe method to permanently seal the Bore. The great sa'angreal were so powerful that using them required special ter'angrealaccess keys which were assembled in an area far removed. The access keys were lost and the Choedan Kal were never used (SaSG).
Though both statues are mostly buried, the tops are visible. The male statue stands near the village of Tremonsien and the female statue stands on the island of Tremalking.
TGH,Ch31 - Verin knows about the giant statue in Cairhien and about its counterpart on Tremalking. She tells Rand that they are male and female sa'angreal. She says that only Elaida, Moiraine, Siuan and the three girls are strong enough to handle the female giant statue. Logain would be fried by the male giant statue.
KoD,Ch22 - The female Choedan Kal on Tremalking melts after the cleansing. The Amayar see this as a sign that the Time of Illusions is over and they commit mass suicide.