In hazy spring sunshine on Saturday, hundreds of young Seoulites turned up at a park by the Han river at the invitation of the city government ​to try to do something many overworked South Koreans never get enough of – ‌sleep.

The Seoul Metropolitan Government staged its third annual spring event, dubbed a power nap contest, from 3pm local time, under a refreshed set of admission requirements for the participants: wear outfits befitting either a sleeping beauty ​or prince, come tired, with a full belly.

For a metropolis that famously runs on ​24-hour shopping malls, competitive hustle and iced Americanos, the underlying exhaustion on the ⁠lawn was palpable.

"Between exam prep and part-time jobs, I survive on three or four ​hours of sleep a night, patching it up with desk naps during the day," said Park ​Jun Seok, who showed up draped in the silken, crimson robes of a Joseon Dynasty monarch.

"I'm here to show off my napping skills, and to demonstrate exactly how a king sleeps," Mr Park, 20, a university student, said.

Nearby, Yoo ​Mi Yeon, 24, an English teacher from Ilsan north of Seoul, stood out in a plush, oversized ​koala-themed onesie.

"I've always suffered from insomnia, I struggle to fall asleep, and wake up easily," she said. "Koalas are ‌famous ⁠for their deep slumber. I came dressed as one hoping to borrow a little of their magic."

Now in its third year, the sleep competition underscores a chronic issue for South Koreans. Data shows that South Korea is one of the most overworked and sleep-deprived nations among the Organisation for Economic ​Co-operation and Development members, ​and, as a consequence, ⁠people post some of the fewest sleep hours.

As the clock struck 3pm and eye masks descended across the park, officials went around to ​measure participants' heart rate to make sure they had a stable reading - ​an indicator ⁠of deep, peaceful sleep.

The winner of the contest was a man in his 80s.

Hwang Du Seong, a 37-year-old office worker, was a runner-up.

"I was completely drained, having done night shifts often on top of ⁠going ​to work everyday plus I also drive a lot ​for work. So when I saw the contest I was determined to sleep to fully recharge amid river breeze, and ​I'm very happy to be placed second place, luckily.”