Libeňský plynojem, Industrial gas holder in Libeň, Czech Republic.

Libeňský plynojem is a spherical gas holder 20 metres in diameter, made of 14 mm steel plates joined by multiple rows of rivets. It stands on eight double-walled steel legs set into concrete foundations, and its surface has an aluminium spray coating that reflects sunlight.

Built in 1932 by Vítkovice Mining and Iron Company, with machinery from ČKD, for Prague's municipal gasworks, it was the first spherical pressure gas holder in the Czech lands. It served only thirteen years; in May 1945 a projectile struck its south side and exploded inside. Repaired, it was handed to the Aeronautical Research and Test Institute in 1949.

Locals call the sphere Koule, and two neighbouring streets, Pod Plynojemem and Ke Kouli, are named after it. Painters and photographers of the Skupina 42 group, including Miroslav Hák and František Gross, used it as a subject, and Josef Sudek, Josef Ehm and Dagmar Hochová photographed it. Bohumil Hrabal, who lived nearby in Na hrázi, wrote about it, and a 2004 exhibition at the U Zlatého prstenu gallery was devoted to the motif.

The site is easily accessible from Libeň and offers good viewing angles from multiple sides, with different perspectives depending on the time of day and lighting conditions. Visiting during daylight hours gives the best opportunity to see the silvery surface and steel structure clearly.

A projectile struck the sphere from the south during the May 1945 uprising and exploded inside; a patch marks that side, while dents from shrapnel remain visible on the north. The tank was nearly empty, so the structure held.