Aerial photo shows people visiting Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows people visiting Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)

Aerial photo shows scenery of Nanhu scenic area in Tangshan, north China's Hebei Province, Oct. 20, 2020. Nanhu scenic area was transformed from subsidence area of Kailuan colliery. (Xinhua/Mu Yu)