mile-high city 

Denver, Colorado, USA.

The elevation of Denver, the capital city of Colorado, USA, is 5,280 feet - the equivalent of one mile - above sea level.

*No relation to the 'Mile High Club'.
*No reference to the legailty of cannabis in the state of Colorado.

Colorado non-native: Why is Denver, Colorado called the 'Mile-High City?'

Colorado native: Because the city of Denver, CO, is literally 5,280 feet above sea level.

mile-high city by MadPupil December 2, 2017