Dover is a coastal town in England’s southeastern county of Kent. It’s a major port for ferries to Calais, in France. Built to repel invasions from across the English Channel, medieval Dover Castle overlooks the town and houses the extensive Secret Wartime Tunnels.

Lisbon is Portugal’s hilly, coastal capital city. From imposing São Jorge Castle, the view encompasses the old city’s pastel-colored buildings, Tagus Estuary and Ponte 25 de Abril suspension bridge. Nearby, the National Azulejo Museum displays 5 centuries of decorative ceramic tiles. Just outside Lisbon is a string of Atlantic beaches, from Cascais to Estoril.

Cartagena is a port city and naval base in the Murcia region of southeast Spain. Founded by the Carthaginians around 220 B.C., the city boomed during the Roman period. Among its many Roman ruins are a 1st-century B.C. theater and Casa de la Fortuna, a villa with murals and mosaics. The Muralla Púnica (Punic Wall) interpretation center houses the remains of a 3rd-century B.C. defensive wall.

Monaco, officially the Principality of Monaco, is a sovereign city-state and microstate on the French Riviera close to the Italian region of Liguria, in Western Europe. Bordered by France to the north, east and west, it is lapped by the Mediterranean Sea to the south.

Ajaccio is the capital of Corsica, a French island in the Mediterranean Sea. A port city on the rugged isle's western coast, it was the birthplace of French Emperor Napoléon Bonaparte in 1769. His ancestral home, Maison Bonaparte, is now a museum displaying family heirlooms.

Mahón, or Maó, is the capital of the Spanish island of Menorca. It’s known for its British-style Georgian houses and sheltered harbor. Santa María Church, with an ornate 19th-century organ, sits on central Plaça de la Constitució. Next to the church, the city hall has a Renaissance facade and a clock donated by the island’s first British governor.

The Port of Gibraltar, also known as Gibraltar Harbour, is a seaport in the British Overseas Territory of Gibraltar. It was a strategically important location during the Napoleonic Wars and after 1869 served as a supply point for ships travelling to India through the Suez Canal.

Portsmouth is a port city and naval base on England’s south coast, mostly spread across Portsea Island. It’s known for its maritime heritage and Portsmouth Historic Dockyard. The dockyard is home to the interactive National Museum of the Royal Navy, the wooden warship HMS Victory, where Nelson died in the Battle of Trafalgar, and HMS Warrior 1860.