The Tag des offenen Denkmals (Day of Open Monuments) is an annual event all over Germany. The day of action has been coordinated by the Deutsche Stiftung Denkmalschutz since 1993. Historic monuments are open to the public free of charge. It takes place on the second Sunday in September and attracts several million visitors each year [de]. The largest cultural event in Germany is the contribution of the country to the European Heritage Days. From Wikipedia
