A city mentioned in My Little Pony Friendship is Magic several times over the years, featured on the official Equestria map, and making a brief appearance in Chapter 8 of Flurry Heart's Baby Scrap Book (see Youtube) is Baltimare, based partially on the real world city of Baltimore, Maryland, USA.
I have an interesting background story for Baltimare. 100 years before the time when MLP Friendship is Magic begins, Baltimare, originally a city in the human world (the Equestria Girls world) is magically teleported to Equestria in the main MLP world, on the shore of the Horseshoe Bay. This feat is accomplished by so-called "gremlins" (actually a group of spirits of chaos from Chaosville, Discord's home dimension).
At first, the formerly human inhabitants of Baltimare are shock that they have transformed into ponies (mostly Earth ponies along with a few unicorns and pegasi). They are also shocked that they can no longer properly digest certain foods (mainly meat, as ponies are primarily herbivores).
Ironically, Baltimare still has statues, pictures, books, and newspapers that still portray the inhabitants of the city as humans, and they are saved as precious heirlooms.
Princess Celestia and other representatives of Equestria's royal regime quickly recognize the supposedly new city of Baltimare in eastern Equestria, and the Princess immediately proclaims the residents of Baltimare as full citizens of Equestria.
By the time of the first season of Friendship is Magic, three generations of ponies have been born and grew up in Baltimare, and a fourth generation of ponies (still young) is being born. Meanwhile, the original inhabitants of Baltimare, the actual humans-turned-pony, were mostly dead, with less than 100 of the so-called First Comers still alive at the time the MLP series begins.
Baltimare ponies can interbreed with "normal" Equestrian ponies, and it has happened pretty often. Indeed, by the time the MLP series is in season 1, most inhabitants of Baltimare can trace their ancestry to both the once-human First Comers and ponies actually born in Equestria.
Culturally, Baltimare ponies are in certain ways different from other Equestrians. Some of them drive steam engine-powered carts on the streets of Baltimare, unlike other ponies who drag carts by hitching up to them and drag them along with foot/hoof power.
Baltimare ponies call their cutie marks "butt marks" or "brands".
Local holidays celebrated in Baltimare have largely mixed with standard pony/Equestrian holidays: Christmas and Thanksgiving with Hearth's Warming Eve, Valentine's Day with Hearts and Hooves Day, and Nightmare Night with Halloween.
Some Equestrian ponies question whether Baltimareans are "real" ponies, and even some Baltimareans question that, too.
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