Königstein castle can be reached by Dresden by the train line S1 (in the direction of Schona). The station is Königstein. From the station you can trek up to the castle or take a toy train and bus for 4EUR.
Königstein can also be reached by boat on the river Elbe from Dresden.
The castle is getaway for the whole day and a good spot for picnics. You can walk up the old castle paths or take an elevator to the top. The charge for entering the castle is 6€ for adults and a concession fee of 4€.
The castle has many permanent and some temporary exhibitions.
Any of the great beers brewed in Saxony.