This combination photo shows a view of Rua das Estalagens, one of the earliest streets in Macao (top, photo by Tang Mengzong, issued on Aug. 26, 1986), and a street view of Macao, south China on Sept. 27, 2019 (bottom, photo by Qin Qing). On Dec. 20, Macao will celebrate the 20th anniversary of its return to motherland. Over the past two decades, the special administrative region has made great strides in economic development and achieved prosperity and stability under the "one country, two systems" principle. Since Dec. 20, 1999, the historic day for Macao, what has changed? And what remains unchanged? Our selection of photos present comparative illustrations of the south China city's past and present. (Xinhua)