PYONGYANG, North Korea — By 8:30 a.m. Sunday, the 50,000 seats in Kim Il-sung Stadium were nearly filled with men in Mao suits and coats and ties, women in dresses and heels, and soldiers in olive-drab hats with crowns as wide as a discus.

Students carried paper megaphones and silver wooden clappers that flashed like flag semaphores and magnified the rhythmic applause, a sound of both welcoming and required exuberance.

In the hazy chill, I stood on the track with about 650 runners from about 30 countries who had come to challenge their preconceptions as well as their endurance.

We awaited the start of the Pyongyang Marathon, a brief opening into one of the world’s most closed and enigmatic countries and surely the only distance race with a promotional video featuring an all-accordion boy band doing a cover of Norwegian synth-pop music.