Castelo de São Jorge, or St. George's Castle, is perched atop Lisbon's highest hill in Alfama, offering both excellent history and views of the city. The castle served as a fortification for the ...

Leilani Osmundson, Digital Producer Though you'll have to trek 30 miles north of Copenhagen to reach Kronborg Castle, this UNESCO World Heritage-listed structure in Helsingør can't be missed.