What is a popular castle for people to go see in Europe?

Kronborg Castle in Denmark is a UNESCO World Heritage Site. It is also the castle that inspired Shakespeare for Hamlet (although he never went there). Neuschwanstein Castle in Germany is very popular with the Americans, and is one of the most visited castles in Europe. The setting is spectacular, as is the castle from the outside, but it is a bit disappointing from the inside, at least to a European like myself. Historically the castle is not that old, it was pretty, but it didn't feel that authentic. I guess it all depends on what you are expecting and what you are looking for, though. I haven't been there yet myself, but Ashford Castle in Ireland is high on my list of places to see. That said, there are quite a few castles in Europe, especially in the U.K, France, and Germany, I would first look around the area where you plan to stay and chances are you will find one not too far away. You can also take a look at this site: http://www.guide-to-castles-of-europe.com/index.html

Try Dover Castle in England, south east in Kent Has a bit of everything from roman lighthouse right up to 2nd world war underground hospital also in Kent there is Leeds Castle, advertised as the most beautiful castle in the world

Stirling Castle in Scotland , it has great history behind it and when you go there you can sorta "feel the history ".

Blarney Castle - Ireland Kiss the Blarney Stone for Good Luck