When my architect friend Westley visits Paris, he doesn’t dawdle in the Louvre or climb the Eiffel Tower. Instead, he goes for a stroll. “I want to experience the city like the locals do,” he once told me. “The idea of crowding around the Mona Lisa with a scrum of tourists just doesn’t interest me.” In other words, Westley is a boulevardier, a “flaneur,” that great French word derived from the Old Norse verb “flana” or “to wander with no purpose.”

But Westley and his ilk do have a purpose: they participate in a city by observing the quotidian flow of street life. Sometimes you can learn more about a place just by watching daily interactions along its thoroughfares than by visiting its monuments and museums, not that there’s anything wrong with museums or monuments.

Initially, I tried to argue. “What? You’ve been to Paris five times and you’ve never visited the Louvre?” But as I grew older and visited the same cities over and over, I came to appreciate the value of wandering with eyes and ears open to the pulse of urban life.

And as Westley once explained, “Why spend a whole day in the British Museum? There’s nothing British in it anyway. Britain happens outside it.” Besides, he insists, exploring a city on foot costs nothing.

So what better place to observe a city’s denizens, to reflect and discover and wander, than along some of the world’s most beautiful boulevards, those wide, tree-lined streets humming with city life?

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Champs Elysees, Paris

On the instructions of Napoleon III, Baron Georges-Eugene Haussmann (1809-1891), the Robert Moses of his day, evicted 350,000 Parisians to lay down 50 miles of new boulevards, strictly regulating the height, color, materials and general design of adjacent buildings, edicts which today give Parisian boulevards their pleasingly uniform appearance. However, this famous street is not part of Haussmann’s legacy. Dating from the 17th century, it runs 1.2 miles from the Arc de Triomphe (definitely worth a climb for the views) to the Place de la Concorde, where the Obelisk of Luxor still towers majestically despite being over 3 millennia old. Look back from the Obelisk to the Arc to see the boulevard at its best.

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Commonwealth Avenue Mall, Boston

I’m a Bostonian by birth so of course I’m provincially prejudiced, but even Winston Churchill called Commonwealth Avenue (“Comm Ave” as we call it) “the grandest boulevard in North America.” Running eight architecturally homogenous blocks from Arlington Street to Massachusetts Avenue in the Back Bay and then westward to Newton, the 200-foot-wide Comm Ave Mall, designed by architect Arthur Gilman in 1856 and inspired by Haussmann’s boulevards, covers 32 acres. Gilman insisted that all houses should sit back 20 feet from the pavement, adding to the avenue’s grandeur and spaciousness. In springtime, magnolia trees grace the Mall with their pink petals; in winter, its entire length glows with artfully lit trees.

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Passeig de Gracia, Barcelona, Spain

Designed by Ildefons Cerda, an urban planner and Barcelona native who also conceived the city’s other boulevards, this artery is embellished by four rows of closely spaced plane trees, tiled benches designed by native son Antonio Gaudi, elegant street lighting, and the city’s most upscale retail outlets. All of which make this lively, mile-long boulevard the most beautiful street in a beautiful city. The central 36-foot-wide sidewalks provide plenty of room for ambling. Stop at No. 43 where one of Gaudi’s most famous creations, Casa Batllo, welcomes visitors 365 days a year (tip: buy an “early bird” admission for 37 euros and you’ll have the place almost to yourself).

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Eastern Parkway, New York City

Created by Frederick Law Olmsted and Calvert Vaux (who also designed Central Park) this 2.5-mile-long, historic landmark in Brooklyn connects Grand Army Plaza and Prospect Park. Six rows of trees spaced 25 to 30 feet apart, and handsome brownstone row houses set back from the street, add to its appeal, and a subway line runs underneath, so it’s easy to reach by public transit. The Brooklyn Museum, anchoring the western limit of the parkway, organizes blockbuster exhibits that rival those offered by New York’s more famous museums. If you visit over Labor Day Weekend you’ll witness the West Indian Carnival Parade.

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Via dei Fori Imperiali, Rome

Built on the orders of fascist dictator Benito Mussolini, the construction of this impressive boulevard, inaugurated in October 1932 with a military parade led by Il Duce himself on horseback, destroyed most of Julius Caesar’s Imperial Forums — ironic since the avenue’s name translates to “road of the imperial forums.” Envisioned to connect Rome’s greatest achievements (whatever wasn’t torn down to build it), this four-lane, tree-lined road is now pedestrianized, over the protests of local residents but to the delight of boulevardiers. Stretching from the Piazza Venezia to the Colosseum, it takes you on a stroll through ancient Roman history.

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Avenida da Liberdade, Lisbon, Portugal

Constructed between 1879 and 1886, variously described as the “Champs Elysees of Lisbon” or “Lisbon’s answer to Fifth Avenue,” the avenida’s 27-foot-wide pedestrian paths, decorated in black and white pavers and intricate mosaics, provide ample room to stroll (walk with care in wet weather since these walkways become slippery). Two rows of trees on either side provide shade from the sun. Nearly every international luxury brand maintains stores on this beautiful street and you’ll find three Lisbon Metro stations along it.

And while I still think museums are worthwhile, the world’s most beautiful boulevards are museums of a kind themselves, tableaux vivants, steeped in history, free for all to explore.