Impossible spaces

This is a stretch of Main Street that transitions between two Pittsurgh neighborhoods. From the street, the houses and storefronts seem impossible, with their faces at odd angles to the pavement. Even in an aerial view the lots seem to be strange and distorted. One house, the middle of a row of three, has a narrow backyard that seems to be the same length as the hose. There's a tree growing in a trianglar lot that seems to share the backs of five separate buildings.

Pittsburgh houses have the added complication of having grown that way. Most of these houses were built between 1875 and 1895. Additions, usually built to accommodate kitchens and bathrooms, extended off the original house.

Do you see that odd-shaped white polygon in the middle? and the three connected structures right above it? What is going on with that building? That has got to be the strangest thing on the block.