Alto de Letras

The climb runs from Mariquita at around five hundred metres to the pass at Letras at about 3,679, which is roughly eighty kilometres of continuous ascent gaining over three thousand metres - by most reckonings among the longest paved climbs in the world, and the one Colombian cyclists cite when explaining where their climbers come from. The gradient is not severe, averaging around four percent, which is what makes it possible at all; the difficulty is duration and altitude. The climate changes completely on the way up, from tropical heat at the bottom through coffee country and cloud forest to cold paramo at the top, where fog and rain are usual. It appears regularly in the Vuelta a Colombia. Traffic includes heavy lorries on a two-lane road.

What's there

• About eighty kilometres of continuous climb - over three thousand metres of gain.
• An average around four percent - long rather than steep.
• Four climate zones on one road - tropical heat to cold paramo.
• A regular Vuelta a Colombia stage - and a training reference for climbers.

When to go

December to March and July to August, the drier windows. A full day.

Good to know

It is a serious undertaking taking most cyclists five to eight hours. The road carries heavy lorry traffic with no shoulder. The top is cold, wet and often fogged in. Altitude affects riders from sea level.

Nearby

Mariquita is at the bottom; Manizales is beyond the pass.

Key facts