Tiwanaku is the most important archaeological site in Bolivia, and standing in the middle of it at nearly 3,900 metres, with the thin air making you light-headed, it is easy to feel why. This was the spiritual and political heart of a civilisation that rose around Lake Titicaca between about 500 and 1000 AD, and at its peak it controlled a territory that reached into modern Peru and Chile. UNESCO inscribed it in 2000.
The main structures are the Akapana, a stepped pyramid that was once faced with stone, the Kalasasaya, a large rectangular platform surrounded by walls, and the Semi-Subterranean Temple, whose walls are studded with stone heads. The Gateway of the Sun, a monolithic arch carved from a single block of andesite, is the best known, with a central figure of a staff-bearing deity surrounded by winged attendants. The stonework is astonishingly precise, with blocks that fit together without mortar, and the Ponce Monolith and the Bennett Monolith are huge carved figures that stand in the courtyards.
The Tiwanaku people farmed the cold plain using raised fields, which protected crops from frost, and built a state that lasted for centuries. Why it collapsed remains a matter of debate, but drought is the leading theory. The Spanish later used many of the stones to build churches and houses, and what survives is only part of what was once there.
The riding is on a good paved highway from La Paz, running across the flat, windswept Altiplano with views of the snowy Cordillera Real. The altitude affects both rider and machine, so go slowly and give yourself time to acclimatise in La Paz first. Fuel is available in El Alto and in Tiahuanaco, though it is best to fill up before leaving the city. The dry winter months, from May to September, are the best, with clear skies, but the nights are freezing. Allow a couple of hours to walk through the site and the museum, and bring a hat, sun cream and warm clothing.