The other day I and a bunch of friends explored some concrete ruins.
I brought along a Mamiya Universal (<–example found on Flickr) medium format camera that Dev gave me, and shot about 4 rolls with a 6×7 film back. (There are other backs, like 6×5 and 6×9).
While the Universal is handy for shooting instant pack film & 120/220, and looks really neat, and is fun to use, …..its a rangefinder, and highly dependent on having the rangefinder calibrated to the lens for accurate focusing. I also have a few Mamiya Super 23s, and I think none of them are totally accurate. This is OK if you just stay away from the widest apertures.
Mine has a 100mm f/3.5 lens. I tried to shoot at f/5.6 or above.
I love using these cameras, but wish they had totally accurate focusing.