Heat.
This place is pretty old, over 100 years. And because of this, it has a good amount of charm - and also hot-water radiator heat. Each room has one of these units, controlled by little thermostats on the water feed. The apartment is surprisingly warm, even with the heaters barely turned on. So, I'm happy it is a cozy place, although I've heard the winters here are fairly mild, rarely dropping below freezing.