Immediately below Baidi City is Kui Men, the entrance to the first of the three gorges of the Yangzi River. The eight kilometre long Qutang Gorge was also known by early western travelers as the Wind Box Gorge. It is the shortest but grandest of them all. The gorge's widest point is 150 metres, "The limestone peaks reach to 1,200 metres high, and the river rushes swift as an arrow through the narrow entrance, pounding the perpendicular faces of the gorge." This gorge is a particularly dangerous stretch during high water levels and has been known to rise up to 72 metres.
In the Tang Dynasty (618 - 907) chains were strung across the river as an 'iron lock' to prevent passage of enemy boats.
In the Song Dynasty (960 - 1279) two iron pillars nearly two metres high were erected on the north side and seven chains, some 250 metres long, were used to block the river passage. Later this was used to enforce the collection of taxes on boats travelling down the river.