Katarina power station, Rectifier station in Södermalm, Sweden.

Katarina power station is a brick rectifier station located on a central street in Södermalm. The building stands out for its tall arched windows and decorative elements inspired by North African design concepts that shape its exterior.

Built between 1902 and 1905 to Ferdinand Boberg's designs, the station converted alternating current from the Värta plant into direct current for Södermalm. Boberg's colleague Gustaf de Frumerie added five window bays in 1918 and another five in 1924. In 1992 Stockholm Energi extended the building toward Östgötagatan, and the older halls facing Björns trädgård were released for conversion into a mosque.

The round ornaments above the Kapellgränd facade depict a cross-section of a high-voltage cable, a detail Boberg used to mark the building's function. Since 2000 the former machine hall, with its culturally valuable tiled walls, has housed Stockholm's mosque and an Islamic cultural centre.

The building faces Kapellgränd 10–14, a short street off Östgötagatan on Södermalm, close to Medborgarplatsen and the Fatburstrappan steps. The 1992 brick extension with Mikael Pauli's two bronze doors faces Östgötagatan, while the older halls open toward Björns trädgård. The mosque entrance is on the west gable, where a narrow extension and minaret were added between 1996 and 2000.

The building was later transformed into one of Stockholm's largest mosques, a surprising shift for a former industrial structure. This change of use shows how architecture can serve new purposes while keeping its historic form.