Musée d'Orsay

The Paris Botanical Garden, founded as the royal medicinal garden in 1626 by King Louis XIII's doctor, contains over 10,000 species. The grounds also include a small zoo known as La Ménagerie, and the Muséum National d'Histoire Naturelle, which includes the Grande Galerie de l'Evolution (where you can see thousands of naturalized animals from all over the world) and the 'Galerie de paléontologie et d'anatomie comparée' (same thing, but with skeletons).

Built in 1717, the windmill is now part of a restaurant of the same name, and is easily visible from the street.

The Jewish quarter, with many small delis and shops. Lively on most days except for Saturdays.

The ancient medieval fortress and prison of the city's island, site of some remarkable medieval royal architecture and the scene of Marie Antoinette's imprisonment in the period leading to her execution in 1793; lots of revolutionary associations.

Housed in an amazing Art Deco building, purpose-built for the 1931 Colonial Exhibition, featuring an elaborate frieze across the front facade that depicts the achievement of French overseas territories. It houses an Aquarium and an Immigration Museum. The aquarium can be seen in about an hour and is popular with families with small children.

One of the truly great venues for the performing arts anywhere in the world, Paris' new opera house actually managed to inspire some neighborhood protest during its planning and construction. Pretty much everybody is a believer nowadays though. Check out the website for upcoming shows, it might even make sense to plan a trip to Paris around one.

The Musée Grévin is a waxwork museum with some 500 characters arranged in scenes from the history of France and modern life.

A sculpture by Auguste Rodin in memory of the French novelist Honoré Balzac. The artwork is sometimes considered the first truly modern sculpture.

A controversial church serving as de facto headquarters of the arch-traditionalist Society of Saint Pius X, who occupied the church in 1977 and have ignored subsequent eviction orders.

One of the largest collections outside Asia of Southeast Asian, Indian, Afghan, Chinese, Japanese, and Korean art.

One of the most eye-popping sights of Paris, the catacombs represent a network of labyrinthine tunnels, first excavated in the Roman period, that now house the remains of over 6 million burials removed here from the various overcrowded cemeteries and charnel houses all over Paris in the late 18th and early 19th centuries. Well worth a visit: the atmosphere is suitably morbid and gloomy (without being too scary), the dark tunnels containing neatly stacked piles of skulls and long bones. There is a limit to the number of visitors allowed within the Catacombs at one time (200 persons). So, if you arrive just after opening, you must wait until someone exits, approximately 45–60 minutes, before anyone is admitted. Steep stairwell on the exit of the catacombs. Can be challenging for the elderly or the unfit. Tickets can be purchased online at a small premium (€29, includes audioguide), allows you pick a date&time and to skip the long line

This charming museum is owned by the French Académie des Beaux-Arts. Its main collection areas, the result of several large donations, include: First Empire art and furnishings; illuminated manuscripts; and Impressionist art, including the largest Monet collection in the world and works by Renoir, Manet, Morisot, Caillebotte and Gauguin.

19th-century bridge.

An industrial design museum in Paris that houses the collection of the Conservatoire National des Arts et Métiers (National Conservatory of Arts and Industry), which was founded in 1794 as a repository for the preservation of scientific instruments and inventions.

The national library preserves collections of historic documents of both French and international origin. It holds 5,000 Greek manuscripts. You can get a day pass to visit or choose to visit only the expositions the library hosts.

An ancient Roman theater, the only surviving above-ground ruins of the Gallo-Roman era in Paris (ancient Lutetia, French Lutèce) apart from the nearby Thermes de Cluny. The theatre could hold approximately 15,000 spectators and measures some 132 m x 100 m. Built sometime in the 2nd century CE, the location of the actor's dressing room, the platform of the stage, and lapidary remains can still be seen. The remains were rediscovered in 1869, when new streets were being built. An excavation was subsequently ordered in 1883. The theatre has been preserved as a quiet archaeological park removed from the bustle of Parisian streets.