Bacon’s idea was a mirror. A long, narrow, shallow plane of water aligned exactly between the Lincoln Memorial and the Washington Monument so that, depending on where you stood, the marble Lincoln dissolved into the sky and the obelisk multiplied into two. Roughly 2,030 feet long, 167 feet wide, 18 inches deep at the edges and 30 inches in the middle. The whole point of those measurements was that they should vanish.

This is a key part of the Lincoln Memorial Reflecting Pool history that often gets glossed over. The pool is not a swimming pool, despite what one architect told NPR last month about “pool guys” refinishing it like Mar-a-Lago. The pool is an optical instrument.