If you only have time for one day trip in Chongqing, China, definitely go to Wulong (武隆) to see the spectacular karst formations.
The UNESCO world heritage site of 3 natural bridges (天生三桥) in the Wulong karst region form the largest natural bridge cluster in Asia, and walking the paved 2.5km route under these massive arches is simply breathtaking. [Fun geek fact: As at May 2018 there are 1,073 UNESCO world heritage sites globally, including 52 in China. 12 of the 52 are natural sites and 3 natural bridges is one of the 12, part of the South China Karst system.]
Wulong karst region (nearest town: Xiannv town 仙女镇, translated as Fairy town) is about 185km (3h) east of Chongqing city. There are four main scenic spots in the Wulong karst region: 1) 3 natural bridges 天生三桥 2) longshuixia gorge 龙水峡地缝 3) Fairy mountain 仙女山 and 4) Furong cave 芙蓉洞. You can cover the the first quite easily in a day trip from Chongqing city, or both 1) and 2) if you are visiting in low season (=no queues). If you want to cover all four scenic spots, an overnight stay will be required.
Read more from source: Chongqing day trip: Wulong karst (3 natural bridges)