At exactly 3 o'clock on Thursday afternoon, a tall, mustachioed man in a cream tuxedo jacket emerged from a brick building behind London's Borough Market. He greeted the group of 20-somethings that had lined up behind blue velvet ropes and, one-by-one, directed us down into what seemed like a dungeon. Ominous organ music scored our descent, and the spiral staircase was nearly pitch black.

"I feel like I'm walking to my death," a man behind me muttered to his friends. Minutes later, we were wearing hooded plastic ponchos and wandering around a thick, white cloud of vaporized alcohol. Some tried to take selfies, others sipped cocktails out of halved human skulls. Everyone was breathing deeply.

"Mixology meets meteorology."

People have been queueing up outside this building since the end of July, when the pop-up bar Alcoholic Architecture opened its doors to the public. Bompas & Parr, the eccentric design firm that created the installation, describes it as "the world's first alcoholic weather system for your tongue" — a place where "mixology meets meteorology." For an entrance fee of £10 (£12.50 during peak hours), visitors can spend an hour drinking potent cocktails and getting lost in "the cloud": a small room filled with vaporized gin and tonic.

Spending 40 minutes in the cloud, according to its creators, is the equivalent of consuming a "large drink." The difference, of course, is that the alcohol enters the bloodstream through the lungs and eyes, which means visitors can get the same buzz with 40 percent less alcohol by volume (and fewer calories).

Prior to opening, Sam Bompas and Harry Parr consulted chemists and doctors about what mixture of alcohol would be safe for the experiment, and how long people could be exposed to it. The goal, they say, was to create a unique, early evening experience, rather than a place for London's club crowd to get completely wasted. That explains the one-hour limit, as well as the project's tagline: "Breathe responsibly."

"We're a real business, so we needed to make sure that everyone who comes through is safe," Bompas said last week by phone from a bar in Amsterdam; coincidentally, he was drinking a gin and tonic at the time.

Harry Parr (left) and Sam Bompas have earned a reputation for outlandish culinary creations. (Stefan Braun)

Bompas and Parr are no strangers to sensory experiments. The duo gained international attention in 2007, when they began creating intricate structures out of jelly. Their other works include a climbing wall made out of chocolate and a bouncy castle of breasts at New York's Museum of Sex.

Alcoholic Architecture began as a short-lived installation in 2009 — the result of what Bompas calls "a funny idea." But its first London run proved popular, inspiring the designers to make it a more elaborate experience. Some bars and companies have offered various vaporized concoctions in recent years, though none are as wholly immersive as what Alcoholic Architecture offers. Its current incarnation will run through early next year, and slots are already booked through September.

A medieval time warp

Walking through the installation is like stepping into a medieval time warp — albeit one with exquisite cocktails and thumping music. The Victorian building that houses Alcoholic Architecture sits directly across from the gothic Southwark Cathedral, on the site of an ancient monastery, and the drinks served at the bar — Chartreuse, Benedictine, Trappist beer — are all concoctions that the monks would have brewed. The entire space has a distinctly dungeon-like feel to it, all stone and coldness, with a stained-glass skeleton portrait in a far corner. Audio of a monk-inspired poem plays on loop in the men's bathroom, recited by an "in-house medium."

Upon entering the basement, imbibers don plastic ponchos and enter the small bar area, where mixologists in white robes stand in front of an ivy-draped backdrop. Some pause to order a cocktail; most head straight through plastic curtains and into an adjacent room, where the cloud awaits.

The first few minutes in the cloud are disorienting, to say the least. White vapor completely fills the room, limiting visibility to less than a meter and forcing everyone to blindly search for their bearings. Muffled dance music is piped in through unseen speakers, with lights alternating between neon hues of blue and pink. After about 20 minutes, I notice that my hands have already wrinkled from the moisture.

Humidity in the cloud is at 140 percent, limiting visibility to one meter. (Marcus Peel)

The atmosphere can be unsettling at first. My primary concern was not bumping into any of the other imbibers, who, in the thick fog, were barely shadows. It's also a small space, and as more people flooded in from the bar, it became even tougher to negotiate. Aside from a young couple canoodling on a ledge, everyone was milling around in atomized friend groups, literally blind to everything else.

According to Bompas, this kind of dense, moist environment is supposed to enhance taste — not only for the vaporized gin, but for the cocktails, as well. "You get this incredible flavor release, you kind of get lost in the flavor a little bit," Bompas said. "If you're in the cloud, you can actually taste the different botanicals expressing themselves in the gin, and the flavors in the tonic water as well."

My unrefined palate didn't pick up on those subtleties, though I did feel a light buzz as the hour drew to a close with a "thunderstorm" of flashing light and noise. It didn't follow the same contours as that familiar, first-drink buzz; it was more subtle and gradual, and true to Bompas' word, I was far from drunk. The bizarre, cramped quarters may have exerted a placebo effect to some degree, but I wasn't the only one feeling light-headed. By the end, what at first seemed like a smoke-filled crypt had morphed into a more typical club scene, full of lubricated chatter, laughter, and dancing. It seemed to be the reaction Bompas was hoping for.

"I just think in a city like London, people are always looking for a new experience and a new way to entertain their friends," Bompas said. "The way we designed it, we give them enough entertaining moments so they can have fun even on a really bad date."

Alcoholic Architecture is open through early 2016 at 1 Cathedral Street, London. Tickets are available here.