Instead of returning to their hometowns, they stayed in Beijing to concentrate on post-production work, delivering video clips in external hard drives among their homes for editing.

"It feels sort of magical to imagine all of the third season's scenes journeying across the capital's empty streets," Yu says.

Weather was a major variable during filming.

They had to wait for the perfect moment to shoot awe-inspiring scenes, such as the sunrise over Yunnan's Meili Snow Mountain and the "sea" of clouds surrounding Anhui's Huangshan Mountain.

"Clouds, fog and mist can create a certain mood or feeling, forging a tone of poetic beauty that contributes allure," Yu says.

"So, we have to be very patient and wait for the best moment."

But such visually stunning conditions make drone flight difficult.

"It's typically recommendable to fly drones on cloudless days with stable winds," Yu says.

Some of the other hardest shoots involved wildlife, such as endangered black snub-nosed monkeys in Yunnan and finless porpoises in the Yangtze River.