Every year, usually during the second weekend of September, the doors of the most interesting monuments, buildings, premises and areas are opened to the public. That includes those that are otherwise partly or totally inaccessible.

The prior aims of this event are: to improve information about other cultures; to protect cultural heritage in the broadest sense of the word; to respect all cultures regardless of their spread and to work for a multi-cultural approach; to regard cultural heritage as an asset which can be used in the struggle against intolerance and bigotry; to support an open and free view of culture, which has an effect not only on economic development, but also on the sustainable development of human society.