NYC is the city that never sleeps, quite literally. Fess up: When was the last time you got a full eight hours, multiple nights in a row? We walk around like semi-zombies, fueled by our cold-brew coffees, wishing there were a more healthful way to get an immediate energy boost. Word reached us that some Masters of the Universe types had a secret—one of a non-pharmaceutical sort. It was whispered that they’d sneak off for a midday nap at YeloSpa, a Midtown business that specialized in such, charging $1 per minute for a reclining-chair snooze in a specially designed room.

Naturally, we couldn’t wait to check it out. All in the name of journalism, of course. But first we reached out to Michael Breus, PhD, a board-certified sleep specialist and the author of two books on sleep, for some advice.

When planning a power nap, he says, the most important consideration is length: “You want to nap for less than 25 minutes, because otherwise your body goes into stage 3–4 sleep. That makes it significantly more difficult to wake up, and it’s likely you’ll wake up pretty groggy.” In that 25 minutes, he says, you’ll get stage 1 and stage 2 sleep, which significantly reduces the homeostatic drive for sleep (aka that craving for naptime). Alternatively, if you can nap for 90 minutes—about a full sleep cycle—you’ll wake up almost completely refreshed. (Of course, if you can spare an hour and a half out of the middle of your day, you’re better off than most people.)

If you’ve got only a short window of time, it’s important to know how to get to sleep quickly. For that, “you have to make sure your environment is conducive to sleep,” Breus says. “Maybe you have eyeshades; maybe you have earplugs. Maybe you’re in a dark room with a blanket.” Another crucial factor is timing. It’s best to nap shortly after lunchtime, between 1 and 3 pm. That’s when circadian rhythms make for a small dip in the body’s temperature cycle, he says, and is when most people feel sleepy.

With all this in mind, we booked a 25-minute afternoon snooze session at YeloSpa, on 57th Street at Fifth Avenue, right between Breitling and Burberry. We were ushered into a dimly lighted room, with music and a scent of our choice preselected, and tucked into a bed with a soft waffle-weave blanket. Bad news, side- and stomach-sleepers: You’re expected to snooze on your back, knees raised (to improve circulation, they say). At the appointed time, we were wakened with slowly brightening lights and a gentle hand on the shoulder.

Is it refreshing? Yes: Our feeling of sleepiness disappeared, and upon returning outside, everything seemed more vivid. It was one of the healthiest indulgences we’ve allowed ourselves recently, and one we can imagine doing regularly.