Illustration done by =jcbarquet. I've currently commissioned him to give some rough environmental sketches of the different far off regions in my 'Expanded' universe for My Little Pony/Equestria.
This illustration is of the home of the Occidental ponies. Based around the 'Civil War' American-era, they make use of toy guns and cannons and are the center of technological steampunk innovation in Equestria. They pioneered the use of 'trains' that enables the transportation of goods and ponies to far away areas quickly and easily. Fort Calhoof's design is inspired from the 'starforts' of the industrial age, with the principal buildings being quite visible in its center (the Manor occupying the center itself, with an adjoining Barracks and Workshop on the outer periphery).
The fort sits on a highly strategic bend in the river known as the Yellow River, which passes all the way down to the Orient area. Fort Calhoof maintains a small fleet of ironclad monitors to patrol the river from baddies that may threaten the vital trade line between the Orient and the rest of Equestria.