House with two rooms
The house is made of 2-dimensional panels, and has two rooms. The upper room may be entered from the bottom face, while the lower room may be entered from the upper face. There are two small panels attached to the tunnels between the rooms, which make this simplicial complex to be contractible.
- Bing, R. H., Some Aspects of the Topology of 3-Manifolds Related to the Poincaré Conjecture, Lectures on Modern Mathematics, Volume 2, 1964