A Bourbon citadel turned Barcelona's largest central green space, the Parc de la Ciutadella certainly isn't short on history. Its 70-plus acres, once the site of Europe's largest fortress, boast plenty of grassy fields, great for picnicking, rambling pathways lined with palm trees, museums, a lake, fountains and the city Zoo. Not much remains of the former fortress, but the arsenal still stands strong, housing the Catalan Parliament and Museu d'Art Modern.
