What is it?

The newly completed Keret House, at just a bit over 4 feet wide, is a temporary home for Israeli author Etgar Keret.

Jakub Szczesny, designer and driving force behind the Keret House installation, in Warsaw. Reuters

Where is it?

Wedged into a sliver of space between two apartment blocks in a section of downtown Warsaw that was the Jewish ghetto during World War II, the house converts what was once a dead alleyway into a living space.

The designer, 38-year-old Polish architect Jakub Szczesny, says he often walked by the narrow gap and became fascinated with the idea of building something there.

"This is a perfect spot for life to be inserted," he said.

Tight Squeeze: Last month, a builder works on the frame of Keret House, located in a passageway between two concrete edifices. European Pressphoto Agency

The front of the finished house measures about 4 feet across and the back measures about 2.5 feet. Maciek Nabrdalik/VII for the Wall Street Journal

Who lives in it?

Officially classified as an art installation, the house was designed to be lived in and function as a sort of urban hermitage for Mr. Keret and other visiting artists.

While working in Israel, Mr. Szczesny met Mr. Keret, whose mother grew up in Warsaw on nearby Jerusalem Avenues. The house was built with funding from public and private sponsors and is operated by the Polish Foundation for Modern Art.

Why is it so small?

The size alludes to the wartime experience of Mr. Keret's father, who survived the Holocaust and the Nazi occupation of Poland by hiding under the floor of another family's house.

How was it built?

Triangular in cross section—wider at the front than at the back—the house is built around a cantilevered steel frame. From the front, it looks like the spine of a narrow, glass-and-metal mesh-sheathed book sitting between two concrete neighbors. In back, a set of retractable steps cascades down to the street.

What's it like inside?

The home has the dimensions of a small yacht or camper. A kitchenette and bathroom are on the raised first floor.

Up a ladder is a second-story sleeping loft and writing space. A window above the narrow bed looks out on the street dotted with dilapidated communist-era blocs.

Write to Marcin Sobczyk at marcin.sobczyk@dowjones.com