The 15th-century site, perched 2,500 metres above sea level, was the site of mass evacuations in January, when landslides forced thousands of tourists to flee by helicopter.
Machu Picchu is the most visited site in South America, a pillar of the Cusco region and the source of 90 per cent of Peru's tourist revenues, according to the country's finance ministry.
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Hollywood actress Susan Sarandon will help formally reopen the Inca city on Thursday.
The railway to the citadel was damaged in hundreds of places by flooding and landslides prompted by the rains that hit the country in late January.
Thousands of stranded foreign tourists were evacuated from the small village of Aguas Calientes, the gateway to Machu Picchu, threatened by rising waters from the Vilcanota river.
The Tourism Observatory had warned that Peru stood to lose up to 0.64 percent of GDP if tourism declined, with particularly serious repercussions for Cusco, where some 175,000 people make a living in the industry.
More than 2,000 tourists from all over the world visit Machu Picchu every day, tourism ministry officials said.
