The remains of ritual offerings found by archeologists show that Isla del Sol was an important local religious shrine long before the arrival of the Incas. When the island came under Tiwanaku control around 500 AD, larger ritual complexes were built and pilgrimages to the island began. Under Inca rule, though, the island was transformed into a pan-Andean pilgrimage destination visited annually by thousands of people from across the empire. The Incas believed the creator god Viracocha rose from the waters of Lago Titicaca and called forth the sun and moon from a rock on the island. They also claimed the founding fathers of their own dynasty – Manco Capac and Mama Ocllo – were brought into being here by Viracocha before travelling north to establish the city of Cusco and spread civilization throughout the Andes. In fact, it’s very unlikely the Incas originated on the shores of the lake. This dynastic myth was probably an attempt to add legitimacy to the Inca regime by associating them with Lago Titicaca and the birthplace of the sun – from which the Inca rulers claimed to be directly descended – as well as providing a link with the pre-existing Tiwanaku civilization that was based on the shores of the lake.
After conquering the region in the mid-fifteenth century, the Incas invested heavily in building roads, agricultural terraces, shrines and temples on Isla del Sol, and establishing the town of Copacabana as a stop-off point for pilgrims. The entire Copacabana peninsula, as well as the sacred islands, was cleared of its indigenous Lupaqa and Colla population and turned into a restricted sacred area, its original populace being replaced by loyal settlers from elsewhere in the empire, who maintained the places of worship, attended to the needs of the astronomer priests and visiting pilgrims, and cultivated maize for use in elaborate religious rituals. A wall was built across the neck of the peninsula at Yunguyo, with gates where guards controlled access to Copacabana (nearly five centuries later the peninsula is still separated from the rest of the mainland by the border between Peru and Bolivia, which follows almost exactly the same line). Pilgrims entering Copacabana would abstain from salt, meat and chilli and spend several days praying at the complex of shrines here before walking round to the tip of the peninsula at Yampupata, from where they would cross over the water to Isla del Sol.
Part of the island’s religious importance was no doubt related to the fertility of its fields. Insulated by the waters of the lake, Isla del Sol enjoys slightly higher average temperatures than the mainland, as a result of which its terraced slopes produce more and better maize than anywhere else in the region. Maize was a sacred crop for the Incas anyway, but that grown on Isla del Sol was especially important. Though most was used to make chicha (maize beer) for use in rituals on the island, grains of maize from the Isla del Sol were distributed across the Inca empire, carried by returning pilgrims who believed that a single grain placed in their stores would ensure bountiful harvests for ever more.