Ruins show 'lost city' of the Incas was part of vast complex

The world's most famous "lost city" - the Inca ruins of Machu Picchu in Peru, found in the early 20th century - was part of a much larger complex, according to sensational new archaeological discoveries.

While investigating a mountain ridge facing the Andean city, an Anglo-American expedition has discovered a previously unknown series of high-status sacred ceremonial buildings scattered over at least a square mile of jungle.

So far, using airborne infra-red reconnaissance and exploration of the jungle itself, the team - led by the British explorer Hugh Thomson and the American archaeologist Gary Ziegler - have found 33 previously unknown buildings. They also found seven others which had originally been located by the American explorer Hiram Bingham in 1912, but the whereabouts of which had been lost, as Bingham left no compass bearings.

Preliminary examination of the ruins suggests that the complex was a large religious centre used for ceremonies and astronomical observations.

The new area istwo miles from Machu Picchu itself. The expedition has identified, as well as the buildings, eight plazas, seven 10ft-highplatforms and a series of walled walkways connecting structures. The buildings include a massive storehouse, a probable sun temple (resembling in several ways the great sun temple in the Inca capital, Cuzco, 45 miles away), and a two-storey observatory, for watching solar equinoxes and solstices.

The archaeologists believe that the complex was probably built by the Inca emperor Pachacuti in the mid-15th century. The complex, known as Llactapata, appears to have been constructed along with Machu Picchu as part of one overall plan. Buildings in both Machu Picchu and Llactapata are aligned with each other and with Mount Machu Picchu, which dominates the site.

The ruined fortress city of Machu Picchu ("manly peak")consists of about 200 buildings at an altitude of 8,000ft. It was probably used to provide seasonal high-status accommodation and some ceremonial facilities for the ruler and his entourage, with room for 1,200 people, possibly during the winter when Cuzco became very cold. Llactapata, on the other hand, appears to have been more ceremonial in nature. The sites therefore complemented each other and formed a greater whole facing each other across the Aobamba River.

Mr Ziegler said: "This is an important discovery which may completely alter our view of Machu Picchu, as the Llactapata site is closely related to it."

Mr Thomson, who has just returned to the UK after four months in Peru, said: "This must be one of the last places left on the planet where major above-ground archaeological monuments are still being located. We are extremely excited by this find."

Archaeologists say the discovery reinforces the need to expand the Machu Picchu Historical Sanctuary's borders to include and protect a wider area. At present the ruins at Llactapata lie outside the protection of the Peruvian National Park Service and so are vulnerable to looters.

The expedition discovered evidence suggesting that looters had been active at the site, despite the fact that archaeologists were unaware of the site's existence.

The Inca ruins are visited by 500,000 tourists every year.

The exploration was carried out with the support of the Royal Geographical Society.