What ancient checkpoints did Baoji pass on the way to Lanzhou?

There is a trend of "one person defends it, and ten thousand people cannot force it". Because of its north-south traffic throat, it has been the "throat of Sichuan and Shaanxi" since ancient times, and it is a battleground for military strategists.

The Big Three Pass is the only fortress in the southwest of Guanzhong. Bashu and Hanzhong have been the throats of Guanzhong since ancient times, and their strategic position is very important. As "Historical Records" said: "The north can't help but beam, and the south can't help but close", so it has become a place valued and contested by military strategists in past dynasties. There have been more than 70 enfeoffment campaigns in history. In 206 BC,

Sichuan-Shaanxi Highway and baoji-chengdu railway pass through the customs, and the Millennium Barrier has become a thoroughfare, and a number of tourist venues have been built. The words "ancient three passes" carved on rocks by predecessors have yet to be verified.