Some say they came from aliens.

The theory lingers in Sichuan's provincial capital Chengdu, where claims of mass UFO sightings about 20 years ago are associated with the otherworldly masks the Sanxingdui culture forged there more than 3,000 years ago.

The masks' telescope-shaped eyes and Spock ears do endow them with sci-fi countenances, while the "beamed-down" notion has been inflated by a knowledge vacuum.

Archeologists have yet to explain the sudden emergence and vanishing of the Shu civilization at the Sanxingdui (12th-11th centuries BC) culture's site - followed by its inexplicable reappearance and second disappearance 50 km away at the Jinsha site, which peaked at about 1,000 BC.

While Sanxingdui has long been a must-see for Chengdu visitors, Jinsha has also been winning acclaim as the staging ground of this historical mystery epic's sequel.

When the excavators of a real estate complex discovered the Jinsha site in February 2001, they realized they'd struck gold - and jade and ivory - and fled with as many relics as they could.

Police dashed after the looters, as archeologists rushed to the site and started peeling earth away in 18 numbered layers.

They retrieved thousands of relics, the most celebrated of which is the Sun and Immortal Bird Golden Disc - a gold foil plate depicting four phoenixes swooping around the sun.

While only 12.5 cm in diameter, this artifact has had a huge impact on the archeological world. It became not only Jinsha's unofficial icon but also the State Administration of Cultural Heritage's official emblem.

Some experts believe the presence of more than a ton of elephant tusks suggests the creatures once roamed Sichuan's plains. Others say the ivory trove is evidence of extensive trade with faraway lands.

The plentitude of boar and deer bones also raised questions about whether the animals had been butchered for meals or sacrifice.

Visitors can hone their opinions while touring the excavation area.

The dig site is located next to a five-wing museum showcasing Jinsha's treasures.

Spans of the museum floor are glass, enabling visitors to walk over partially buried relics. One wing's corner is a story-high jumble of pottery shards that was a Jinsha-era kiln.

Millennia-old relics are presented in futuristic displays such as holographic animations, depicting period jadeware making techniques.

The mostly exhumed human skeletons of several Jinsha adults and children are displayed beneath glass near the exit.

The ruins surrounding them reveal that while they may not be extraterrestrials, they certainly came from a very different world.

China Daily