This combination photo shows people watching a performance at Clube Militar (Military Club) in Macao, south China (top, photo by Bi Yuenian, archived on Aug. 4, 1993) and dancers performing on street during the International Youth Dancing Festival in Macao, south China on July 20, 2019 (bottom, photo by Cheong Kam Ka). 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)