Two previous hospital-employers were old facilities (100 years old or so). Back in the day, they had dormitories for the nursing students who were required to reside in the dorms with the old communal bathrooms and showers.
At both, the old dorms had long been made over to office/storage space but they had retained THE TUNNELS. I visited THE TUNNELS for the fun. To the un-initiated, the underground tunnels connected the dorms to the hospitals for the student nurses to use to quickly traverse the grounds esp in inclement weather. Remember, the students used to run the wards 'back in the day' on the late shifts, holidays, weekends, bad weather, etc. They were a routine source of labor for the hospital (it was just part of the understanding that a student was part of the hospital). The old dorms have been downed, but I'm unsure what they could do with the tunnels.
Also, many old state psychiatric facilities are architectural wonders. I believe Trenton (NJ) Psychiatric Hospital was built around 1865 and the other state psych/DDD facilities are old also (Marlboro was the newest, 1952 ish; since closed. It had tunnels, too, so on-campus residential staff could get around to the cottages.)
I know Philadelphia also has old, old (1700's old) institutions. The old buildings are just phenomenal for their ages.