Keret House, in Warsaw, Poland, was built as an art installation in 2012. Designed by architect Jakub Szczesny, the building has gained popularity as the narrowest house in the world, measuring 3.02 ft (92 cm) at its thinnest point and 4.99 ft (152 cm) at its widest point.

Its called the Keret House after the Israeli writer, Etgar Keret, who is the building's first tenant.

The building contains two floors, one bedroom, a kitchen, a bathroom and a living room. The house has custom water and sewage technology, and so, is not connected to the city water system.

Occupants have to use a ladder to travel from floor to floor. Retractable stairs make up for the entry. When closed, these stairs become the living room.

Despite being used as a residence, this building is considered an art installation since it does not follow the Polish building codes.