The spandrel was the space between the arch and the rectangle. Put an arch inside a rectangular frame and the leftover triangles in the upper corners are the spandrels. The spandrel was not designed. The spandrel was the consequence of putting a curved thing inside a straight thing. The spandrel was the leftover. The accident. The space nobody planned for that became the space everybody decorated. The best art lives in the spaces nobody planned.

The Romans filled the spandrel with sculpture. A winged victory in the left spandrel. A river god in the right. The spandrel became a gallery because the human eye does not like empty triangles. The empty triangle asks to be filled the way an empty corner asks for a musician. I stood in a lot of empty corners. The corner was a spandrel. The city planned the buildings and the buildings created corners and the corners were leftovers and the leftovers became stages. Washington Square Park is a spandrel. The city built a grid and the grid left a gap and the gap became the most important park in Greenwich Village.

The spandrel on a steel building is different. The curtain wall panel between the top of one window and the bottom of the window above it. That horizontal strip is the spandrel panel. The spandrel panel hides the floor slab and the fireproofing and the ductwork. The spandrel panel is a mask. Behind the mask the building is ugly. Concrete and steel and spray-on insulation that looks like popcorn on a ceiling. The spandrel panel covers the ugly and presents the glass and the glass presents the sky and the sky presents nothing and the building disappears into its own reflection.

The biologist Stephen Jay Gould wrote about spandrels. He said evolution creates spandrels the same way architecture does. Build an arch and the spandrel appears. Build a brain for survival and language appears. Language was not the plan. Language was the spandrel. Music was not the plan. Music was the spandrel. Every good thing the human brain does might be a spandrel. A leftover of a structure built for something else. My whole career was a spandrel. The city built itself and left gaps and I filled the gaps with noise.

The modern facade has no spandrels because the modern facade has no arches. The rectangle contains no curves and the absence of curves creates no leftovers. The glass curtain wall is all rectangle. Every inch is planned. Every inch is accounted for. There is no space between the curve and the straight because there is no curve. A building with no leftover space is a building with no room for surprise. The spandrel was the surprise. The architect did not plan the sculpture in the corner. The sculptor found the corner and filled it. Take away the corner and the sculptor has nowhere to stand.

See also: Pilaster, Quoin