Under Pachacutec, the most eminent Inca king, the empire attained its greatest territorial extension, stretching over parts of present-day Ecuador , Colombia , Bolivia , Chile and Argentina in addition to the whole of Peru, Pachacutec unified the empire by adopting a single language, Quechua, and building an impressive network of roads – the Inca Trail – providing rapid comunications between the realm's main localtions.

It was during this Inca's reign that Prince Inca Tupac Yupanqui organised a maritime expedition that eventually reached Polynesia. Accounts of that voyage were collected by the chronicler Sarmiento de Gamboa and were vindicated, centuries later, by Thor Heyerdahl 's 1947 Kontiki expedition, which sailed from Peru to Polynesia in a similar raft and following the same course as those used by the ancient Peruvians.