More than 80 years ago, another adventurer came to these jungles, looking for lost cities, buried treasure and mystical ancient objects with strange powers.

BBC: The kingdom of the crystal skull

"We have not found any ancient objects linked to the context, and because the paintings are on ravine walls and in the rainy season the sediments are washed away, all we have is gravel, " said archaeologist Gustavo Ramirez, from the Mexican National Institute of Anthropology and History (Inah).

BBC: Cave paintings in Mexico: Carvings uncovered in Burgos

In ancient times, however, such objects played a more significant role, with the intaglios used as seals (because these carvings were incised rather than raised) and the cameos employed as symbols of the state.

WSJ: Museum Exhibit Review: Gems of the Medici at the Bowers Museum

Eva Beuys, the artist's widow, still lives in the city, and the gold-hued "Palazzo Regale" installation, with its evocation of ancient burial rituals, coupled with objects recalling the artist's own life, is of supreme importance, says Ms. Temkin.

WSJ: Touring Beuys-World in Germany's Lower Rhine

The two institutes have developed compact and portable x-ray devices capable of analysing the structure and chemical composition of ancient bones, buildings, and art objects in a non-destructive fashion.

UNESCO: Basic Sciences

Perhaps if he had, like Egyptologist Howard Carter, discovered gold, jewelry and other fabulous funerary objects during his exploration of the ancient overland road to China rather than musty books of Buddhist sutras (even if they did include the world's oldest known printed volume), his lasting fame might have been secured.

CNN: Books

Some 100, 000 visitors are expected to view the around 8, 000 objects from 95 French and international dealers in an enormous range of disciplines, including ancient, modern and Asian art, jewelry, weapons, ceramics, glass, furniture, books and tapestries.

WSJ: Book Is a Collector's Item

This El Dorado-inspired looting of gold has meant that the vast majority of precious pre-Columbian gold objects have been melted down and the real value of these artefacts as clues to the workings of an ancient culture have been lost forever.

BBC: El Dorado: The truth behind the myth