When my art student daughter in London sent an e-mail saying she'd stood in line to get tickets to the slides at the Tate Modern, I assumed it was an exhibit that had something to do with photographic slides.

How wrong I was.

The slides are the smooth metal kind. The ones that children frequent in parks. Only these are slides on steroids: twisting, turning vehicles that rise like Medusa's hair through the museum's five-story-high open hall. More than 600,000 thrill seekers have ridden the slides since the show opened Oct. 10; the exhibit was recently extended by a week, and its final day is April 15.

So how did playground apparatus, albeit super-size versions, get into Britain's national museum of modern art? Designed by German artist Carsten Hoeller, "Test Site" is the seventh in the Unilever Series, which each year has a different artist figure out a way to use the museum's cavernous Turbine Hall. Hoeller's installation initially consisted of five slides of various heights. (One slide was removed in January to make way for another exhibit.)

In a museum brochure, Hoeller explained his work as "sculpture you can travel inside."

"Slides deliver people quickly, safely and elegantly to their destinations, they're inexpensive to construct and energy-efficient," Hoeller said. "They're also a device for experiencing an emotional state that is a unique condition somewhere between delight and madness. It was described in the '50s by the French writer Roger Caillois as a 'kind of voluptuous panic upon an otherwise lucid mind.' "

Having an affinity for existing in a state between delight and madness, I put the exhibit on my list of things to do during a recent visit to London.

Arriving about 11 a.m., I headed to a window to pick up the free, timed tickets required for the taller slides. Lines can get long during midday. (Tourists don't realize the museum is open late on Fridays and Saturdays, so going after 7 p.m. on those days means shorter lines.)

I felt a bit surrealistic as I listened to the attendant instruct me about placing my feet in a canvas sack and folding my arms across my chest.

I launched myself down the enclosed corkscrew tube, feeling like a fish in a bowl as I peered through the tube's clear plastic top at people staring at my descent. The welding along the structure's joints painlessly whacked my back, adding to the feeling of plummeting through space. Twelve seconds later, after traveling a curving 182-foot route down the 43-foot drop, I was shot out of the slide and onto a black pad, exhilarated and out of breath.

Later in the day, another quote from Hoeller came to mind: "The state of mind that you enter when sliding, of simultaneous delight, madness and 'voluptuous panic,' can't simply disappear without (a) trace afterwards."