A great piece over at slice about some old coal ovens. The pizza addict in me is very interested. Some great background:

Coal ovens come in several formats, but the oldest are the cavernous mason-built bread ovens from the turn of last century. These beasts are so massive that they were either built out into a building’s back yard or into the foundation itself, extending beyond the building’s footprint. When a bakery went out of business, it was much easier (and cheaper) to slap a wall in front of the oven than doing any kind of demolition. This means that old bakery ovens are very likely still in place, just waiting to be discovered. Here’s a quick rundown of five dormant coal-burning ovens in New York.

Coal ovens do make for awesome pizza. Though they are apparently very demanding to operate. New York Daily News also notes that they aren’t actually banned like the myth states. I can’t imagine retrofitting a NYC building to add one though. I’d imagine it would be expensive if it wasn’t already part of the structure. Not to mention depending on coal deliveries.