10. Aragonese Castle, Ischia
Ischia is a small volcanic island that has become popular over the years due to its unique architecture and proximity to Naples. To get to Castello Aragonese, you have to travel by boat from the city. The reason this castle was built in the first place was to protect the inhabitants against pirates. Although it was fortified in the 15th century by Alfonso V of Aragon, everything from the original structure remains intact.
In spite of the fact there have been times when it was closed for maintenance, it is usually open to the public on a daily basis. The boat fare can cost anything from 20 to 30 euros, depending on the dimension of the ship. Ferry tickets are quite affordable.