Salt Mine - Wieliczka
Situated 10 km from the city centre of Krakow. The Mine is the heritage of the work of several dozen generations of miners. Today, the Wieliczka chambers are known mostly as one of Poland’s most visited tourist sites. There is underground infrastructure you can visit as well as many events during the year. New Year’s Eve Concert, Chopin concert series, Jazz Meetings, New Year’s Eve Ball, others.
If you think about unusual events in a remarkable place it could be nice idea.