The concept is simple: keep the city's museums open in the evening and lay on shuttle buses to help visitors move from one to the next, sampling the treasures on view. The 40-plus museums hope to win new visitors, while, for those too busy to go to a museum during the day, the Long Night offers a chance to sample the full range of the city's treats in one go.

Compared to Berlin, Munich and the other German cities which have mounted such events, Cologne's most important collections are clustered close together in the city centre. The two main institutions are the Wallraf-Richartz Museum, with an outstanding collection of Medieval and Renaissance art, and the Roman-German Museum, which houses artefacts from the days of Roman settlement in the city. The Applied Art Museum, the Ludwig Museum (20th-century art) and the Mikwe (excavated remains of a medieval Jewish ritual bath) are also conveniently located in the centre.

Shuttle buses to the north, south and west make it easy to reach a number of other interesting museums, such as the Museum of 1960s-1970s Design, museums for non-European art and even the Stollwerck Chocolate Museum. Lots of extras are usually organised as well, including masses of DJs and concerts of jazz, world, modern and baroque music.

Started in 2000, the event has become a huge success and is now a must in the city's autumn calendar.