Kahlenberg, Mountain summit in Döbling district, Vienna, Austria.

Kahlenberg is a mountain summit rising 484 meters above Vienna, offering views of the city, the Danube River, and the surrounding vineyards from viewing terraces. A church stands at the top where visitors arrive after climbing or taking the bus.

The mountain played a key role in 1683 when troops launched an attack from its slopes against forces threatening the city. This event became a turning point in Vienna's defense.

The summit church is St. Josef, built for the Kamaldulenser hermitage founded after Ferdinand II acquired the mountain in 1628. The houses that grew around its Chapel of Saint Joseph became Josefsdorf. The mountain's earlier names, Sauberg and Schweinsberg, referred to the wild pigs in its oak forests.

The location is easily reached by public transport or hiking trails, and visitors should prepare for changeable weather, especially during rainy months. Sturdy footwear is advisable if planning to walk.

Around 1920, Albert Einstein, Otto Neurath and other mathematicians and physicists met on the Kahlenberg to make the first plans for what became the International Encyclopedia of Unified Science. The project later grew into a large international publishing venture.