Lake Titicaca sits at 3,812 metres above sea level, making it the highest navigable lake in the world — a claim that sounds like tourism copy until you're standing on its shore and the water stretches to the horizon under a sky that feels closer than it should. The Bolivian side of the lake is accessed through Copacabana, a small town on a peninsula about 155 kilometres from La Paz and 3.5 hours by bus on a good day. Buses depart from near the Cemetery district throughout the morning; the journey includes a short ferry crossing of the Strait of Tiquina, where you board a small boat while the bus drives onto a separate barge.
Copacabana itself has a large white cathedral — a place of genuine pilgrimage for Bolivians — and a lakefront lined with trout restaurants. The trout is the right thing to order: freshwater fish from the lake, cooked simply, as good as you'll eat anywhere in the country. From Copacabana you can take a boat to Isla del Sol, the island where Inca creation mythology locates the birth of the sun. The boat ride is an hour each way; the island has no cars, some good walking trails, and pre-Inca ruins at the northern end. A day trip from La Paz to Copacabana is possible but rushed — the bus back leaves in the afternoon, which gives you two hours at the lake. Better to stay one night, which allows a morning boat to Isla del Sol in the calm before the tourist boats arrive.