Aerial photo taken on Dec. 19, 2017 shows the Ruins of St. Paul's and Monte Fort in Macao, south China. Macao Special Administrative Region of the People's Republic of China is on the southwestern side of the Pearl River Delta. Although it is a densely populated region, with a population of about 670,000 and an area of some 33 km2, Macao has been putting efforts on ecological protection. Macao has over 20 urban parks or gardens, four rural parks and three wetland ecological zones. Its unique geographical location provides migrant birds valuable resting and wintering grounds where more than 100 species of birds forage and inhabit here. From Sept. 22 to 24, the "Macao Day" event is held at the ongoing Beijing International Horticultural Exhibition. (Xinhua/Cheong Kam Ka)