This is a city entirely filled with pegasi because it is made out of clouds and floats in the air. Any non~enchanted non~flying being that attempts to walk around here will fall through the cloud floor below. A strong unicorn can grant you the ability to walk on clouds or give you wings for a short period of time, so you may be able to visit. Pegasi guards fly a little bit below the city to catch any pony who does fall through, however, so if your enchantment wears off too soon, you'll be safe. They were issued on the day of the young fliers competition when the unicorn Rarity almost died, so they've been trained in such time.