Even into the future with advanced technology, the ponies continue with airship terminology - it is practically an airship base because it is little known from France in 1900-1914 that “airports” meant for airships had deep and wide ditches for the airships, which are brought in and out of the hangars with the gondola hull in the ditch itself.
 
From the show we know that they built their airships sheltered from the wind where the mountain sides provided significant shelter from the wind forces, and then launched them out into a precipice rather than letting them rise into the air. This port facility for aircraft can be considered a continuation from older times when there were still airships, by continuing with the same infrastructure as before.
 
The actual terrain around the city is unusual, as if on a different continent far from Equestria.

Woo, details