There are two houses on Cooper undergoing interesting infill treatments. This older house has been jacked up and put onto a new foundation. The two openings at the foundation facing the street were for the steel beams holding up the house. The process: the house is supported from underneath with cribs, the joists cut off around the old stone foundation, and new joists sistered onto the old ones, along with additional supporting beams. Then the house is lifted, new foundation poured, and the house lowered down again.
In this case, the new foundation under the old house has few if any windows, so it will not be used for living space, which strikes me as curious to put in a new foundation and raise the house without using the space underneath for more than storage. There is a new foundation at the rear, which will be either a big addition or another housing unit(s).
This type of infil preserves the streetscape while intensifying the neighborhood by building in the back yards.