Over a decade has passed since the London Millennium Footbridge, the River Thames’ most terrifying — or, for some, strictly nauseating — pedestrian crossing, was closed to the public and reopened, two years and £5 million in repairs later, in a decidedly less “oh dear lord, I may never make it across this bridge alive” form.

Now, the River Thames can once again boast a pedestrian crossing — a high-level walkway, to be exact — that’s capable of quickening pulses, triggering cold sweats and prompting full-on anxiety attacks.

The twin horizontal walkways are certainly not a new addition to the Victorian Gothic London landmark otherwise known as the Tower Bridge. Rising 138 feet above the Thames, the tower-connecting walkways are part of the bridge’s original design and an integral part — from an engineering standpoint, they help to anchor the span — of the world-famous structure.

What is new are potentially petrifying glass bottom floors within the walkways that enable pedestrians to peer straight down onto the bustling roadway — or the river itself when the bascule/suspension bridge is up. It’s a spectacular bird’s-eye vantage point, no doubt, but also one that those with more delicate constitutions or debilitating cases of acrophobia will most likely avoid.

The walkways themselves have a fascinating history. While popular when the bridge first opened in 1894, it didn’t take long for Londoners to decide that they were wildly impractical to use on a regular basis. After all, crossing the Thames via the Tower Bridge walkways involved hiking up a daunting staircase in one tower, crossing the (at the time uncovered) walkways and then descending a second set of stairs in the opposite tower.

A far less intensive option was to just wait for the span to close and cross the bridge at road level. With little regular foot traffic, the walkways were a lonely and rather dodgy place overrun with pickpockets, prostitutes and other shady characters. Within several years, the Tower Bridge walkways had become London’s most spectacularly sited back alleys and, in 1910, they were closed to the public.

In 1982, the walkways reopened as part of the Tower Bridge Exhibition, an admission-charging tourist attraction complete with a museum housed in the bridge’s towers.

Thanks to the sweeping views enjoyed from their interiors, the Tower Bridge walkways have remained a heavily trafficked tourist magnet since their reopening (the addition of elevators and fully covered walkways helps). But apparently, the one thing that’s been missing all along is an element of fear.

Earlier this week, the 37-foot-long glass-bottomed section of the West Walkway opened to the public. The East Walkway is due to open in December.

The fact that you can now mill about over the River Thames on (perfectly safe to walk on) three-inch-thick glass plates will most certainly appeal to thrill-seekers and those looking for a singular London experience, vertigo be damned. (In all honestly, it's not that high up). But for those who go out of their way to avoid standing on see-through surfaces at extreme heights (see also Chicago’s Willis Tower, Toronto's CN Tower, the Eiffel Tower, the Grand Canyon Skywalk) may steer clear of the Tower Bridge Exhibition’s so-called “wow project.”

You’d think that maybe they’d offer both a glass-bottomed and a non-glass-bottomed option, but that’s not the case.

Still, officials are confident that the £1 million overhaul, funded by the City of London Corporation, will boost visitor numbers. “We did a lot of consulting with the public, we don’t want to scare people off — we are not a scare attraction," Chris Earlie of the Tower Bridge Exhibition tells The Guardian. "We are trying to provide something which has never before been seen here before.” Earlie does admit that "I do a lot of climbing and adventure sports but, even for me, the first time was a bit difficult."

The Tower Bridge Exhibition currently attracts 600,000 annual visitors.

And then there’s the question of appropriate dress. While the Tower Bridge’s roadway is lifted 850 times each year at designated daily times to allow vessels to pass, it remains predominately open to vehicle and foot traffic. This means that even though there will be hundreds of folks spying down onto the bridge’s roadway from the walkway above, there will be just as many people in the bridge's road-level pedestrian lanes peering up. Officials, however, reassure female visitors that they can feel free to wear skirts without worry that they’ll inadvertently be putting on a free show for a rapt audience below.

“This was a consideration at the outset of the design process,” explains a Tower Bridge Exhibition spokesperson to the Telegraph. “Pedestrians can look up but the walkway is not directly above them, it’s a little bit off-centre. The layers within the glass, combined with careful control of the lighting system within the walkway between day and night time, address this potential issue.”

Issues of modesty aside, do you think you'd fork over a few pounds (about $13) to brave the River Thames' newest attraction?

Via [The Guardian], [The Telegraph]

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Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.