Overview: Using cutting-edge, 3D laser-scanning technology, structural engineer Steve Burrows leads his team of experts into the Peruvian jungle to scan the sacred Inca city of Machu Picchu, asking three main questions: How did the Inca build a city atop a mountain ridge? How were the terraces constructed? And how did they supply water to the city? Join the team as they turn back time and decode the past.

DVD Verdict: OK, from the off, those not in the know should know exactly what the to-be-discussed Machu Picchu actually is. Well, Machu Picchu is a 15th-century Inca site located 2,430 metres (7,970 ft) above sea level. It is located in the Cusco Region, Urubamba Province, Machupicchu District in Peru.

As we quickly learn from the documentary, it is situated on a mountain ridge above the Sacred Valley which is 80 kilometres (50 mi) northwest of Cuzco and through which the Urubamba River flows. Most archaeologists believe that Machu Picchu was built as an estate for the Inca emperor Pachacuti (1438–1472). Often mistakenly referred to as the "Lost City of the Incas" (a title more accurately applied to Vilcabamba), it is the most familiar icon of Inca civilization.

The Incas built the estate around 1450, but abandoned it a century later at the time of the Spanish Conquest. Although known locally, it was not known to the Spanish during the colonial period and remained unknown to the outside world before being brought to international attention in 1911 by the American historian Hiram Bingham. Most of the outlying buildings have been reconstructed in order to give tourists a better idea of what the structures originally looked like. By 1976, 30% of Machu Picchu had been restored; restoration continues today.

Ergo, this incredible sacred city has had everyone wondering - especially those that have seen it up close and personal - just how the still-standing building frames made from huge boulders were moved into place. I mean, the wheel had not even been invented yet! A second question was “why were there so many terraces?’ And, a third question was “how did the 1,000 or so inhabitants get water to drink, wash and plant, when the city was on top of a mountain 8,000 ft above sea level?”

There have been studies but now a new form of laser photography can actually provide the answers. This is the goal of the laser photo experts – who call themselves “time scanners” - and they have done these analyses for other historic sites. Thus, the results are all here now for Machu Picchu in this PBS series Time Scanners” (53 minutes). This is a Widescreen Presentation (1.85:1) enhanced for 16x9 TVs.