Can anyone tell me what castle this is and where it is located?
As per the comments, it appears to be Veliki Tabor Castle, in Croatia.
Veliki Tabor (Croatian: Great Camp) is a castle and museum in northwest Croatia, dating from the middle of 15th century. The castle's present appearance dates back to the 16th century.
Most of the castle was built by the Hungarian noble family of Ráttkay, in whose ownership it remained until 1793.
It is located in the region of Zagorje near Desinić, 8 km (5.0 mi) west of Pregrada, 334 m (1,096 ft) above sea level. It has around 3,340 m2 (36,000 sq ft). The castle is owned by the state, which manages it as a museum and a tourist site.