The earthquake that ravaged Sichuan province last year caused massive damage, especially to the areas surrounding its capital, Chengdu. But one place that escaped severe damage was Sanxingdui, an archaeological site famed for its bizarre discoveries, located northeast of the city. Sanxingdui is home to the Sanxingdui Ruins Museum, which features a collection of bronze and golden artefacts unearthed in the region between 1986 and 2001, the final remnants of a mysterious culture centred along the Yellow River. Many of the figurines unearthed in the area look as though they could have come from Mexico or from Native American burial pits - but not from anywhere on the mainland. Their origin remains a mystery. The culture that produced them is thought to be 5,000 years old, and the makers of the figurines had mastered metallurgy (especially bronze) years before rival civilisations, creating statues and casts far removed from traditional Chinese design. Even more mysterious is why Sanxingdui, just an hour by road from Chengdu, is not more widely known. Xie Weifan and Ling Shuyun, a young couple visiting from Guangdong, find the figurines baffling. 'I've never seen anything like these statues, except maybe in Canada,' says Xie. 'They remind me of American Indian sculptures.' In 1929, a farmer discovered a large pit of buried jade at Sanxingdui. It wasn't until the 1960s that the site was fully surveyed - by which time many pieces had fallen into private collections. In 1980, a government archaeological team began a systematic excavation of the site, and in 1986 they discovered the first of two large pits full of jade, bronze heads, pointed helmets, masks and other headgear. The Sanxingdui Ruins Museum, purpose-built for the collection, consists of two main galleries, some distance from each other on extensive grounds studded with gardens and canals, plus one smaller gallery. Gallery One features an introduction to Sanxingdui, and the ancient 'moon-brilliant' civilisation of the Shu dynasty. Gallery Two's structure consists of a spiral ramp winding upwards and inwards, with exhibition halls opening off the ramp. On the lower levels are collections of striking masks and busts unearthed from the Sanxingdui sites, including the oldest 'life-sized' statue of a person, at 2.6 metres and 180kg. Elsewhere, a tableau resembling an Aztec sacrificial altar is a startling artefact. In the centre of the spiral, a scale model of a sacred bronze tree found in the pits - which researchers believe is themed around the Fusang tree of Chinese mythology - dominates the museum hall. The yin-yang circle on the museum grounds is a performance space half-surrounded by tiered seating. 'Go stand in the circle and shout out loud,' says Ling from Guangdong. I stand on the white circle, and shout. Nothing happens. I stand on the black circle and shout, and still nothing happens. Then I stand on the junction of the black and white segments and shout, and my voice suddenly reverberates as though a big bronze bell has been placed over my head. The effect is surreal and intoxicating. The yin-yang circle is just one of the many mysteries of Sanxingdui still awaiting an explanation.