The Inca civilisation was an ancient civilisation in South America on Earth. They, like many other civilisations, were inspired by the Exxilons. (PROSE: The Left-Handed Hummingbird)
Inca Priests used the Great Power to grant superhuman powers. (PROSE: Doctor Who and the Daleks)
When the Great Bairn landed on Earth, it was found by the Incans. They built the Tomb of the Bear around it. When the Eleventh Doctor believed the Great Bairn was in danger, he stole it from the tomb in 1934 and delivered it to David Kershaw in 2009. (PROSE: Snowfall)
The Eleventh Doctor once met the Cybermen in an Incan temple in Peru. (GAME: The Mazes of Time)
Machu Picchu was an Incan city in Peru. (COMIC: Hitching Point, The Doctor and the Nurse) By 1911, it was considered to have been lost. When the Tenth Doctor, Heather McCrimmon and Hiram Bingham visited Machu Picchu, they discovered that Incasaurs had opened a portal to the city, in order to escape their world, and in so doing had created a time hole. (COMIC: Hitching Point)
In 1977, Brigadier Lethbridge-Stewart investigated an Inca pyramid in South America. (AUDIO: The Cloisters of Terror)
In the Doctor's TARDIS there was an Incan quipu. (PROSE: Sanctuary)