Festung Marienberg 
Description
Built high on a hill overlooking the city from the opposite bank of the Main the fortress was home to the Prince Bishops before the construction of the Residenz and afforded them protection from the locals who wanted to get rid of the Prince Bishops and become a free Imperial city like Nuremberg. You can walk around the fortress site free of charge, but to go into the buildings - which house a couple of museums - there is an entrance fee (according to all the guide books and websites the museums are only in German and not particularly worth visiting)
Charge
Free
Getting There
Latitude: 49.789902; Longitude: 9.920068
What3Words: trek.entitle.paper
