Denver, Colorystal. A city that lies between Applewoods, Canterlot, and Manehattan. The city were the 6 mares/6 friends and their foals/children live in. And just south of the city is Castle Rock, CY and Colorystal Springs, CY. Denver is a neighboring city of Canterlot.
 
The Clock Tower in the city holds the most secured and secretive powerful source that lies underneath the city. And Princess Celestia, Princess Luna, and Twilight Sparkle know about the source, they are trying to hide the source from the Outside worlds and trying to find a guardian to guard the city and the nation from the evil force of Queen Chrysalis, Lord Tirek, Cozy Glow, and Grogar.
 
Then Princess Celestia, Princess Luna, and Princess Cadance came with a plan of build three super scrapers in Denver to use them as Mixed-Use buildings and at the top of the buildings are conferences rooms for planning etc.
 
And the city of Denver would appear in the first episode Fan Fiction of My Little Pony: Denver Girls.
 

 
Edit (Here’s The Large Version)
 
https://www.deviantart.com/denverbrony/art/Denver-Colorystal-in-the-Nation-of-Equestria-LV-840011922?ga_submit_new=10%3A1588270090