This is one view of what you see when you look through the crack in the door.

Duchamp assembled his final work, Étant Donnés, from 1946 to 1966. It was installed in the Philadelphia Museum of Art after his death. The work consists of a wooden door. When you step on the linoleum to peek through the crack in the middle of the door, lights suddenly illuminate the scene on the other side.

The full title, in English, is 
Given: 1. The Waterfall, 2. The Illuminating Gas.

The female torso is made of pig skin stretched over a frame. Although the viewer can see the whole torso, no face is visible.