The Aymara people had settled Isla del Sol for centuries before the Incas invaded and most structures in the area credited to the Inca were built by them. This includes the Inca Staircase and the Inca Fountain, a spring spouting from three pipes: El Condor representing heaven, La Puma representing earth and La Serpiente representing the underworld. Isla Del Sol was a sacred place for the Aymara and extremely important in Inca mythology, being the place were Viracocha, the sun god, created the first Inca man and woman. Even today it is held in reverence by the Aymara people and is home to 3500 of them.
Reference: http://www.gang-gang.net/nomad/andes/andes09.htm