Hankou Tunnel located on Xinxiang-Jincheng Expressway, constructed by China State Construction (CSCEC) has been certified by Guinness World Records as the world's longest spiral tunnel, with a total length of 4,457 meters. 

 The Hanko Tunnel ranges in altitude from 784 meters to 893 meters, with an maximum elevation difference between the tunnel entrance and exit of 109 meters, and has a minimum radius of 700 meters.

https://english.cscec.com/CompanyNews/CorporateNews/202405/3787429.html