Last June, city workers in Paris started cutting apart the layers of colorful padlocks that had been spreading across the panels of the Pont des Arts bridge like an invasive vine. The “love locks” began appearing on the bridge around 2008, and city officials complained that they’d damaged the historic structure and obscured views of the Seine. The couples who proclaimed their love this way—usually by etching their initials on the locks and throwing the keys into the river—might have said the authorities were being unromantic.

They certainly have the numbers on their side: love locks are found on bridges throughout the world, including on New York's Brooklyn Bridge, Moscow’s Luzhkov Bridge and the bridge on Lotus Peak in Huangshan, China. The origins of the custom aren’t clear, but may have to do with a World War I Serbian tale in which a teacher is abandoned by the object of her affection, and young girls in her town who hope to avoid the same fate begin “locking up” their love on a local bridge.

Bridges have often been subject to superstitions, perhaps because they are a literal passage between two places, and often symbolize movement from one stage of life to the next. In many parts of the world it’s considered unlucky to be the first person to cross a bridge; the idea is that the devil, envious of the human ability to create a construction so complicated, will take the soul of the first living creature to make its way across. Workers sometimes leave money in the plaster of a new bridge to protect it and ensure good luck, perhaps a remnant of a rumored earlier custom involving human sacrifice. Some people touch the roof of their car, or spit, when driving under a bridge while a train or other vehicle is passing, supposedly to make sure it doesn't collapse, although this seems both ineffective and unhygienic. 

Some other interesting bridge-related customs around the world include the following. 

1. Wish Locks, Fengyuan, Taiwan

In a variant of the love lock practice, residents in the Fengyuan District of Taiwan have taken to attaching "wish locks" to the wire mesh fence of a pedestrian overpass at the city's train station. Some who do so reportedly believe that trains passing below create a magnetic field that accumulates in the locks and fulfills the wishes written on the outside of the padlocks. Examples include “[I wish to] successfully pass university entrance exams,” “I want happiness” and “[give me] eternal love.” Some of the locks are hung in pairs and are known as "heart locks." Authorities have removed the locks on several occasions, but they keep springing back up, and the location has developed into a tourist destination. However, in 2012 it was announced that that the bridge was going to be torn down for an elevated railway. After local outcry, the bureau in charge of the bridge announced that it would relocate the structure and turn it into a public arts project.

2. Touching Saint John of Nepomuk, Charles Bridge, Prague

LenDog64, Flickr // CC BY-ND 2.0

On Prague's beautiful Charles Bridge stands a statue of Saint John of Nepomuk, vicar-general of the archdiocese of Prague and now patron saint of Bohemia. According to tradition, the priest perished when Wenceslaus IV had him drowned in the Vltava river after he refused to divulge the queen's confession. The statue was erected in 1683, on what was believed to be the 300th anniversary of the saint’s death in 1383, but, because of a copying error in the 15th century, was actually the 290th anniversary. It was supposedly placed at the precise point where poor John was thrown into the river. Touching it is said to bring good luck and a swift return to Prague. Others say the saint was thrown into the river a little further toward the Old Town, where a cross with five stars stands on a parapet. Touching the cross and stars with your left hand while making a wish is supposed to make the wish come true.

3. Greeting the Fairies, Isle of Man

The Isle of Man, located in the Irish Sea between Great Britain and Ireland, is home to a number of supposed fairy bridges, but the one most popular with tourists is on the A5 road between Douglas and Castletown. Local custom dictates that those crossing the bridge are supposed to say "hello, fairies" to bring good luck, and failure to do so supposedly brings misfortune. Some take the custom even further, leaving messages and gifts (such as teddy bears, flowers, fuzzy dice and underwear) by the side of the road. That might be a wise approach—the local fairies aren't of the delicate, sweet variety, but are said to be two feet tall and grumpy.

4. Good Luck Animals on The Bridges of St. Petersburg

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At least two of St. Petersburg’s 200 bridges have their own special customs. On Ioannovsky Bridge, the city’s first, tossing a coin at the feet of a metal sculpture of a little hare that stands on a wooden pillar in the water is supposed to be good luck. (The statue commemorates a local legend about a hare who saved itself from a flood by jumping into Peter the Great’s boot.) On the Bankovsky Bridge, there’s a second opportunity to cultivate good fortune: putting your hand on the feet of one of the bridge’s lions while making a wish is supposed to ensure that your wish comes true as you cross the bridge. 

5. Kissing at the Crim Dell Bridge, William and Mary College

benuski, Flickr // CC BY-SA 2.0

Plenty of college campuses have romantic spots, but few are as picturesque, or as storied, as the red-and-white Crim Dell footbridge at William and Mary. Campus lore says that two people crossing the bridge while holding hands will be friends for life, while a couple who kisses after crossing the bridge will be together forever. A variant of the legend says that if the couple breaks up, the woman has to push the man over the bridge, or she’ll face life alone. And anyone who’s decided to give up on love and be forever alone need only cross the bridge by themselves, which supposedly ensures life-long solitude.

6. James River footbridge on the Appalachian trail

Rebecca Sudduth, Flickr // CC BY-NC 2.0

The James River Footbridge is the longest footbridge on the Appalachian Trail, and the sweaty, exhausted hikers who make that trek reportedly have a tradition about jumping off it. (It might be the closest thing some of them get to a shower for a while.) Unfortunately, it might not be one of the trail’s safer customs—at least one local has died jumping off the bridge, and climbing it is now prohibited.

7. Stari Most in Mostar 

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The stunning Stari Most (Old Bridge) is a landmark in Mostar, as well as all of Herzegovina. First built under the Ottomans in the 16th century, it was destroyed during the wars of Bosnia and Herzegovina in the 1990s, but reconstructed with UNESCO help in 2004. For local men, jumping off the bridge and into the frigid water of the Neretva is an old tradition: the first recorded jump from the bridge was in 1664. It's a dangerous leap, and fatalities have resulted, but tourists who want to give it a go can sign up to try it under the guidance of the Mostar Diving Club.

8. Driving Sheep Over London Bridge

diamond geezer, Flickr // CC BY-SA 2.0

In London, freemen have the traditional right to drive sheep and cattle over London Bridge. The right was originally granted to allow them to bring livestock into the city for sale. Over the past several years, Lord Mayors of London have exercised the right by driving flocks of sheep over the bridge as a stunt to raise money for charity, angering some animal rights campaigners. Animals have also been driven over the bridge to mark the start of London Architecture Week, bring attention to the rights of older citizens, and promote fundraising for the restoration of Canterbury Cathedral, among other causes.

9. Kissing Bridges, USA

In some parts of rural America, including Virginia and Indiana, covered bridges are called “kissing bridges” or “courting bridges” because the privacy offered by the roof makes them a perfect place to kiss your sweetheart. Smooching your beloved while passing through is also said to bring good luck. For kids, the “kissing bridges” are sometimes known as “wishing bridges,” and anyone with enough self-control (and lung power) to hold their breath the entire length of the bridge is said to have a wish granted.

10. Measuring in Smoots, Harvard Bridge 

Oliver Smoot enjoys the unusual honor of having his own body used as a unit of measurement. In October 1958, members of MIT's Lambda Chi Alpha fraternity devised a pledge prank in which they used Smoot to measure the length of the Harvard Bridge. (Smoot was supposedly chosen because he was the shortest pledge, and his last name sounded kind of scientific.) The obliging Smoot lay down and got back up repeatedly across the bridge while his pledge brothers painted marks every ten "Smoots" (one Smoot is about 5 foot 7 inches). According to their final calculations, which were painted onto the pavement, the bridge was 364.4 Smoots, "plus or minus an ear." The ear was intended to provide a margin of error, since the fraternity brothers knew their methods weren't precise. The Smoot marks have survived, and are re-painted by incoming members of the Lambda Chi Alpha fraternity each year. They've been preserved through renovations on the bridge, and were celebrated during a Smoot Day bash on October 4, 2008, the 50th anniversary of the original measurement. Incidentally, Oliver Smoot went on to have a career in measurement, eventually becoming chair of the American National Standards Institute and serving as president of the International Organization for Standardization.