You can wander, sit, watch, nap, and wander again, throughout the night. Hey, if it's routine you wanted, you would have stayed home. At the least, there may be people within who will assist you with energy and pleasure. If you need a place to stay, you need a place to stay. Besides, some wonderful stories may be born in such places.
Guidebooks often mention possibilities.
Try them out. Just walk through one at night and look around. If you find a spot that seems safe, quiet and unlikely to provoke the authorities, score. Travelers who might otherwise sleep outside head for the stations when it's raining. There's nothing quite like catching a needed shower in the rain at night in a Bulgarian cemetery.