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Actually, if you don't mind sleeping on the floor, have a second bed, or have a large couch, a St. Bernard would be a great apartment dog. (NOT a puppy, but full-grown.) Large dogs, so it may seem odd but they don't move much once they stop being a puppy. They look like rugs basically. You would likely save it's life if you found one at a rescue near or in a city since most people wouldn't think of a dog that size as an apartment dog. Just walk it twice a day, if you have a casual work environment walk it to work, show it the couch, and then walk it back home. They are low energy dogs for the most part, great baby sitters, and definably one to frighten evil-doers, even without opening an eye.
Yes, some of the breed are sure to want more exercise or want to play in the snow, but that is just the personality. My mom's liked to sit outside but didn't move much except to roll over or occasionally lay on her back and wiggle. But my guess is that a St. Bernard found in a city shelter wouldn't mind not being allowed to sit in a yard and do nothing.