Step into the new Tilt! attraction on the 94th floor of the John Hancock Center and at first nothing happens.

You are holding big metal bars. You are peering through a full-length window. But you know what is about to occur, and your insides, you are not ashamed to say, are like a crowded butterfly garden.

And then there’s a sound ­— think noisy dentist’s office, or airplane engine at the gate — and the eight-window chunk of wall you are clinging to begins to quit its right-angled orientation to the massive skyscraper around it.

You and the wall and the other fools at the other windows are pitched slowly forward, and you begin to think about your mortality and America’s long legacy of engineering successes. You think about the city elevator inspectors who evaluated this thing, and you wish that one of them were here alongside you, his presence the most reassuring safety certificate of all.

Once upon a time in tourism, a commanding view from way on high was attraction enough. But recent years have seen an escalation in the race to induce vertigo. Operators at the Grand Canyon and the Willis Tower, also in Chicago, have installed glass overhangs so that visitors can step out past precipices. And now there is Tilt!, billed as unique in the world. You, really, are in no position to argue.

At 20 degrees from vertical, your body tells you it should be falling. Looking down, you see your presumptive target: Chicago’s Chestnut Street, or, with the right wind and a bit of a leap and a soar, the top of the Water Tower Place building across the street. Your knuckles match the white in the nearby clouds.

At 30 degrees, the full extension of Tilt!, you could let go and become a giant bug on a giant windshield, except that, unlike such bugs, you would remain sensate. Also, you are on the inside. As the mechanism pauses to let you take it all in, you are slowly acclimating to this challenge to your equilibrium.

Taking it all in

Where once you thought “yikes” or “zounds” ­— or other expressions of wide-eyed amazement tinged with fear — now you are beginning to take in the city that spreads beneath you: the actual Water Tower that survived the Great Chicago Fire, Michigan Avenue, the park behind the Museum of Contemporary Art.

This view, as you are pitched forward like the figurehead on the prow of a ship, extended out over 1,000 vertical feet of air, is breathtaking. It could be the fresh perspective stealing your wind, but it is more likely the result of your lizard brain telling you your body, right now, is supposed to be plunging into those locales.

But your human brain is winning the argument. This is safe. This is well thought out, by people who know how wind, metal, glass and hydraulics behave. This is, really, very cool.

Tilt!, 360 Chicago, the new name for the old John Hancock Observatory, makes a bold move toward being better at putting metaphorical lumps in tourists’ throats than any other place in town.

There’s the Ferris wheel at Navy Pier, combining vintage charm with modern height. There’s the Ledge, the single name for the four glass boxes that jut 4 feet out from the western wall of Skydeck at the Willis Tower.

But Tilt! does something new, something I found entirely enchanting. It moves you. It nudges you forward, then pauses, then tilts you forward some more. It makes a substantial thing ­— the majestic Hancock tower — suddenly whimsical.

Engineering on view

If a window wall rotating outward is playful, there is nothing light about the way it is built. It is a box of steel, 31,000 pounds of it, powered by a hydraulic motor and three big pistons known as hydraulic actuators.

Just as the Hancock wears its support pieces like a bandit’s guns, on the outside, visitors to Tilt! can see the giant nuts and bolts and the heavy beams doing the work of keeping them safe; they can touch a glass panel that shows what the three-layer, tempered, laminated structural glass used in the windows is like. Tilt! wears its engineering on its sleeve, coming across as a mechanized, dare we say it, slow-motion thrill ride.

Apparently, we do not dare. “We tend not to use the ‘R’ word. We call it an ‘experience,’ ” said Jennifer Hesser, 360 Chicago’s director of operations.

The experience lasts maybe 5 minutes in the Tilt! area along the observatory’s south wall, and 75 or so seconds in the mechanism itself. The charge is $5 extra atop standard 360 entrance fees of $18 for adults, $12 for children 3-11. (The $5 is an introductory rate; to be determined are how long it will last and what the normal charge will be.)

Having Tilt! in 360 Chicago means tourists are more likely to visit there, rather than go to the Signature Lounge one floor above and look at the views from that establishment for the price of a cocktail.

I enjoyed the whole thing, but still, I was grateful that they hadn’t decided to call this non-ride, say, Tilt-a-Whirl! Just plain tilting was plenty.