Photo taken on Feb. 2, 2021 shows rooms of a tree hotel, located about 150 kilometers south of the Arctic Circle, northern Sweden. The tree house hotel located in a dense pine forest some 150 kilometers south of the Arctic Circle has become a frequent visitor spot since its opening in 2010. (Photo by Wei Xuechao/Xinhua)

Photo taken on Feb. 2, 2021 shows a room of a tree hotel, located about 150 kilometers south of the Arctic Circle, northern Sweden. The tree house hotel located in a dense pine forest some 150 kilometers south of the Arctic Circle has become a frequent visitor spot since its opening in 2010. (Photo by Wei Xuechao/Xinhua)

Photo taken on Feb. 2, 2021 shows a room of a tree hotel, located about 150 kilometers south of the Arctic Circle, northern Sweden. The tree house hotel located in a dense pine forest some 150 kilometers south of the Arctic Circle has become a frequent visitor spot since its opening in 2010. (Photo by Wei Xuechao/Xinhua)

Photo taken on Feb. 2, 2021 shows the aurora Borealis or Northern Lights seen from a tree hotel, located about 150 kilometers south of the Arctic Circle, northern Sweden. The tree house hotel located in a dense pine forest some 150 kilometers south of the Arctic Circle has become a frequent visitor spot since its opening in 2010. (Photo by Wei Xuechao/Xinhua)