Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province. (Photos: Xinhua)

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.

Photo taken on May 25, 2019 shows the 326-meter-high Bailong Elevator, the world's highest outdoor elevator, shrouded by fog at the Wulingyuan Scenic Area in Zhangjiajie, central China's Hunan Province.