Ring the right doorbell, duck into an unassuming alleyway, take an unmarked staircase, and you may suddenly find yourself in one of Paris' hidden wonders: a tiny village-like warren of cobblestoned streets lined with shops, ancient Roman ruins, a secret Alpine garden, a peek-a-boo view of Notre-Dame, a sobering war memorial, a glittering church lined with stained glass windows. Some of these are famous; many have fallen through the cracks of the modern city. Here's how to find them.
Crypt Archéologique de Parvis de Notre Dame - The archaeological excavations beneath Notre Dame's square date back to the Roman and Celtic eras, yet few of the hundreds of thousands of tourists who flock to the cathedral even know it's there.
Holocaust Memorial - An evocative, sobering spot tucked beneath the vest-pocket park behind Notre Dame cathedral at the very eastern tip of Île de la Cité.
★★ Sainte-Chapelle - A cathedral of colored light comprises this medieval stained glass masterpiece hidden amongst drab buildings on Île de la Cité.
Sewer tour - A fascinating tour through the city's underbelly (and no, it's doesn't smell like you'd think it would).
Alpine Garden in the Jardin des Plantes - An Alpine microclimate in a sunken garden hidden in a formal Parisian park.
Institut du Monde Arabe - A glorious view of Notre Dame from the back (from the terrace of a cool post-modernist building with neat exhibits on Near Eastern culture).
Roman amphitheater - Little remains of this 2,000-year-old performance space in a tiny, hidden park called place Emile Mâle in the Latin Quarter. However, the very idea of such a slice of ancient Rome suriving to become a tiny park through which Parisians walk their dogs is pretty amazing.
The catacombs of Paris - The old limestone quarries of Paris became a dumping ground for excess dead bodies in the 1700s. The bones from the skeletons have been used to create walls, corridors, and grisly decorations in these underground tunnels...
★ Musée de l'Orangerie - One of my favorite hidden sights in Paris, packed with Impressionist paintings and preserving in its basement two rooms fitted with 360 degrees of Monet waterlillies... » more
Alley villages - Paris has these tiny villages-within-the-city, small tangles of quiet cobbled alleyways called passages lined by shops and artist ateliers, typically hidden from view and entered from a unremarkable doorway along an otherwise busy boulevard.