There’s a bit of a disconnect there. Large, herd-dwelling herbivore that evolved on and for steppe and tundra, that needs large quantities of grass forage to survive, and that roams a natural range of hundreds of square miles–how does that fit into the human metropolis?
The answer is: surprisingly well. But it takes some human ingenuity to work.
Space in cities is at a premium. If there is room for horse pastures or greenways or parks, these tend to be reserved for the elite who can afford to pay the price for a scarce commodity. At the same time, horses are needed to carry riders, pull coaches and carts, haul loads, and generally turn their strength and speed to human uses.
When an animal is transport, there’s no room for sentimentality. His health, both mental and physical, is only relevant insofar as it improves or impairs his usefulness. He may be happier in a pasture, but his job is in the city.
City dwellers with the means and the space to maintain their own riding or coach horses had stables in or near their houses. Those who could not afford to keep horses at home might rent space in a livery stable–as many horse owners still do–or simply rent horses from the livery. Carters, vendors, and cab drivers might live beside or above their animals, in houses or lodgings that did double duty for horses and humans.
The rich might house their horses in elegant stables with stalls large enough for the horse to turn around or lie down–loose boxes or box stalls–but even the wealthy and many or most of the rest would be more likely to keep their horses in as small a space as possible. The minimum would be a standing or tie stall: basically, a slot into which the horse would be inserted for safekeeping between jobs. It would be barely wider than the horse–two or three feet, four at most–and only slightly longer than the horse’s head, neck, and body. He would be tied by the head to a ring or bar in the wall, and restrained behind by a rope or chain.
Since the working horse would be out for much of the day and possibly part of the night as well pulling a cab or delivering goods or carrying riders on various errands, his stall, where he would be fed and watered and hopefully sheltered under a roof, would be a kind of refuge. He might even, with care, be able to lie down and rest, if his tie rope was long enough.
When he was out working, he would be expected to cope in all weather. If he was lucky he would have a blanket or rug in cold or wet weather, especially while standing in between delivery runs. He would rarely be taken under a roof and relieved of his harness; he would be expected to be ready to go out again at a moment’s notice. In hot weather, he might be sponged off, and he would be given extra water to keep his system from shutting down.
Equine digestive systems being what they are, a horse needs to eat and drink early and often. Smart horsekeepers in urban settings would bring along a nosebag (made of canvas or similar tough fabric or leather, designed to fit over the nose with a strap over the ears or attached to the bridle) filled with whatever grain or concentrated fodder happened to be available–oats or barley would be common–or carry a supply of hay or cut fodder.
There would also be ready access to water, either carried in the vehicle or supplied by the city in troughs or cisterns or fountains. If the carter or cabbie wanted to keep his valuable and essential horse going, he would make regular refueling stops, and make sure the quality of the fuel was as high as he could afford.
In addition to fuel, in the medieval and postmedieval West, especially on cobblestones or various forms of paving, horses would have been shod with some form of metal shoes. Leather boots were in use in ancient Rome among other places and eras, but whoever figured out that metal plates or rings or rims could be nailed safely and painlessly onto horses’ hooves created a revolution in horse transport. Now a horse could travel many more miles for many more days or weeks with much less wear and tear on the feet, and last much longer and in better condition.
Horses in cities created whole industries for their support. Someone had to grow and process and transport their feed, and sell it to the horses’ owners or managers. Someone else had to mine and forge metal for shoes and harness (buckles, bits, stirrups, even saddle trees and horse collars), and then create the different items–sometimes with great artistry.
Horse harness, everything from strap goods to buggy whips, was big business. In fact the advent of the motor car caused the buggy-whip business to collapse–and so created a metaphor for the effect of new technology on the support systems for the older and unrelated technology. Companies still make horse tack and buggy whips, but they’re much more of a fringe industry now, more for the hobby crowd than for daily use and transport.
People were also needed to train the horses, manage their stables, buy and sell them either privately or in horse fairs and markets–and of course someone had to breed new ones, usually on stud farms in the country.Young horses have to move in order to develop properly, and need space to run. They can be raised in stalls or small spaces, but their muscle and bone development will suffer and they may not stand up to the rigors of daily work.
Retirement was not always an option for city horses. Many literally died in harness; others succumbed to disease or injury. If they were very lucky they might be retired to pasture–maybe on or near the farm where they were bred. More likely once they were no longer useful they were put down, and their bodies would be put to further use as meat, leather, tallow, lye, glue, even fly whisks and paintbrushes.
There’s one other aspect of urban horsekeeping that tends to get literally swept under the rug: manure disposal. A lot of fodder goes in, and most of it comes back out, stripped of the nutrients the horse needs to live. In a city full of working horses, that’s tons of manure every day–and if the climate tends to be wet, the mud will get very bad very quickly.
Hence, street sweepers. Someone has to clean up the manure and carry it off. Where it goes depends on how much space there is for disposal, whether and how soon the culture realizes that dumping it in or near water contaminates the water supply, and what use might be made of it: composted for gardens, dried and compacted to fuel cook fires and heat dwellings, hauled out of the city and spread on fields for fertilizer, and so on.
Which is an advantage horse manure has over car exhaust: it may be a pollutant, but it’s also extremely useful. And when composted, it produces potassium nitrate, a key component of gunpowder–an ambiguous blessing, but definitely important to the march of human progress.