3 Best Sights in Canal St-Martin and République, Paris

The once-forgotten canal has morphed into one of the city's trendiest places to wander. A good time to come is Sunday afternoon, when the Quai de Valmy is closed to cars and some of the shops are open. Rent a bike at any of the many Vélib' stations, stroll along the banks, or go local and cuddle quayside in the sunshine with someone special.

In 1802 Napoléon ordered the 4.3-km (2.7-mile) canal dug as a source of clean drinking water after cholera and other epidemics swept the city. When it finally opened 23 years later, it extended north from the Seine at Place de la Bastille to the Canal de l'Ourcq, near La Villette. Baron Haussmann later covered a 1.6-km (1-mile) stretch of it, along today's Boulevard Richard Lenoir. It nearly became a highway in the 1970s, before the city's urban planners regained their senses. These days you can take a boat tour from end to end through the canal's nine locks: along the way, the bridges swing or lift open. The drawbridge with four giant pulleys at Rue de Crimée, near La Villette, was a technological marvel when it debuted in 1885. In recent years gentrification has transformed the once-dodgy canal, with artists taking over former industrial spaces and creating studios and galleries. The bar and restaurant scene is hipster central, and small designers have arrived, fleeing expensive rents in the Marais. Canauxrama ( www.canauxrama.com) offers 2½-hour boat cruises through the locks (€25). Embarkation is at each end of the canal: at Bassin de la Villette or Port de l'Arsenal.

One of Paris's younger and more exciting contemporary-art venues combines innovative exhibits with live musical performances and a multimedia space that features a library, movies, and free video games. Think of it as a smaller, more interactive Centre Pompidou. La Gaîté Lyrique occupies three floors of a 19th-century theater—remnants of which are visible in the café upstairs.

Science buffs should not miss this fascinating place, Europe's oldest museum dedicated to invention and technology. It's a treasure trove of wonkiness with 80,000 instruments, machines, and gadgets—including 16th-century astrolabes, Pascal's first mechanical calculator, and film-camera prototypes by the Lumière Brothers, fathers of modern cinema. You can watch video simulations of groundbreaking architectural achievements, like the cast-iron dome, or see how Jacquard's mechanical loom revolutionized clothmaking. Kids will love the flying machines (among them the first plane to cross the English Channel) and the impressive display of old automobiles in the high-ceilinged chapel of St-Martin-des-Champs. Also in the chapel is a copy of Foucault's Pendulum, which proved to the world in 1851 that the Earth rotated (demonstrations are staged daily at noon and 5). The building, erected between the 11th and 13th centuries, was a church and priory that was confiscated during the Revolution, and, after incarnations as a school and a weapons factory, became a museum in 1799. Most displays have information in English, but renting an English audioguide (€5) helps. If you're arriving via the métro, check out the platform of Line 11 in the Arts et Métiers station—one of the city's most elaborate—which is made to look like the inside of a Jules Verne–style machine, complete with copper-color metal walls, giant bolts, and faux gears.