Petit Palais, Paris
(permanent collection, free; 011+33-1-53434000)
This Beaux Arts building—with its impressive columns and crescent-shaped courtyard—would be extraordinary even if empty of the 1,300 paintings and objets d'art on display. Its masterpieces come from the likes of Courbet, Monet, and Rodin.
Don't miss: The pomme de pin ("pinecone") goblet by noted de signer René Lalique—the clear glass prettily shimmers blue.
Palazzo Barberini, Rome
(about $7; 011+39-06-32810)
Completed in 1632, the palazzo has a stunning collection of Renaissance paintings, including Raphael's famous "La Fornarina," which is thought to be a portrait of his young mistress, and Caravaggio's "Judith Beheading Holofernes."
Don't miss: The frescoed ceiling, "Triumph of Divine Providence," by Italian artist Pietro da Cortona—the extravagant suns, angels, and linking of the Barberini family to heaven epitomize Baroque excess.
FOR LITERATURE LOVERS
This gallery showcases some of the world's most important books, maps, and papers, including two 15th-century Gutenberg Bibles (Gutenberg's mechanical printing press changed the way books were made), pages from Leonardo da Vinci's notebook, and original music manuscripts composed by Handel, Schubert, and Beethoven. True-blue Beatles fans will love seeing the handwritten lyrics to "Yesterday," penned by Sir Paul himself.
Don't miss: Magna Carta—the 13th-century English charter of political rights is one of the most celebrated legal documents in English history. You can put your nose to the protective case to see the scribes' teeny script; then give your peepers a rest with a look at the enlarged portions also on display.
FOR ARCHAEOLOGY ADMIRERS
Pergamon Museum, Berlin
(about $11; 011+49-030-20905577)
The city's most-visited museum (made up of three main departments) ranks alongside other well-known European sites when it comes to classical antiquities and items from the Near East. Jaw-dropping sights include ancient architectural structures, rebuilt from original stones and other materials. The indoor Market Gate of Miletus (constructed in 120 c.e.) is a 55-foot-high example of ancient Roman architecture, and the brilliantly colored Babylonian Ishtar Gate (575 b.c.e.) is a 47-foot-high edifice of blue-glazed tiles and golden, sculpted dragons and cattle.
Don't miss: The namesake Pergamon Altar—the colossal, three-story, open-air stone altar is from the ancient Greek city of Pergamon.
National Museum, Copenhagen
Exhibits in this rococo mansion trace the Danes from the Ice Age to the present day. Viking artifacts include silver coins and jewelry, small Thor's hammers, and runic stones that commemorate the dead.
Don't miss: The 3,400-year-old "Chariot of the Sun"—the tabletop-size bronze statue depicts a horse pulling the sun across the sky.