Lake Feneketlen, Urban lake in District 11, Budapest, Hungary

Lake Feneketlen is an artificial pond in Budapest's District 11, between Villányi út and Kosztolányi Dezső tér. It covers 1.1 hectares, has a perimeter of about 500 metres and a depth of 4–5 metres. Its elongated, kidney-shaped basin lies below the Szent Imre Church, and a fountain throws up a wide spray of vertical jets in the middle of the water.

The lake formed in 1877 when clay was extracted for a brick factory at Kosztolányi Dezső tér, leaving behind a water-filled depression. This accidental creation eventually became a recreational asset for the surrounding neighborhood.

The open-air stage on the lake's bank was built on a former rubbish tip; its designers were Pálfy Ferenc, Studer Antal and Vitkovits István. A memorial plaque with the name of the designer and construction supervisor was fixed to the wall by the lake at its inauguration. Nearby stand a reclining boy figure, a small stone bear and a statue of Kosztolányi Dezső brooding over his volume Mágia.

The area is easily accessible with walking paths around the water and open facilities available for use throughout the day. Coming by foot or bicycle is convenient given the location in a residential neighborhood.

The lake's basin holds Oligocene Kiscell clay whose pyrite content forms a concentrated bitter mineral water. Because of this, a thermal jump layer typical of deep lakes develops, and the strong hydrogen sulfide content long prevented life from establishing in the water.