Every year on the second Sunday in September, the Open Monument Day is being held nationwide.
This year, Mainberg Castle will also participate, but only virtually.
To visit, you need to go on their website: https://www.fv-schloss-mainberg.de/
The website provides ZOOM Client, which lets you partake in 30-minute visual tours which run from 13:00 – 17:00 on 12 Sep 2021 (Central European Time).