the region, including the First Affiliated Hospital of Sun Yat-sen University, a leading hospital with over 3,000 beds. Several world leaders in translational medicine are based in GBA, such as the lung cancer authority Professor Yi-Long Wu (vice-president of the Guangdong General Hospital and Guangdong Academy of Medical Sciences, and a director of Guangdong Lung Cancer Institute). Overall, GBA has over 200 universities, producing many college and advanced degrees graduates — over 570,000 college students a year graduates only in Guangzhou. Within the GBA, Hong Kong hosts the highest density of top universities globally. Times Higher Education lists as the Top 5 of them the University of Hong Kong (ranked place 39 worldwide in 2021), the Chinese University of Hong Kong (ranked 56 worldwide in 2021), the Hong Kong University of Science and Technology (ranked 56 worldwide in 2021), the City University of Hong Kong (ranked 126 worldwide in 2021) and the Hong Kong Polytechnic University (ranked 129 worldwide in 2021). Infrastructure and transportation GBA is rapidly evolving into the dynamic world-class city cluster connected with the modern transportation network featuring Huangpu Bridge, Guangzhou-Shenzhen-Hong Kong High-speed Railway, Hong Kong-Zhuhai-Macao Bridge (HZM Bridge), Nansha Bridge and Guangzhou-Shenzhen Intercity Railway. There are also massive ongoing infrastructure projects underway. Among them – construction of Guangzhou-Zhanjiang High-speed Railway, Gangzhou-Shenzhen Highspeed Railway and Guangzhou-Shanwei-Shantou High-speed Railway. Further step in GBA's infrastructure development is establishment of airport clusters. Five main airports – Hong Kong International Airport, Guangzhou Baiyun International Airport, Shenzhen Bao'an International Airport, Macau International Airport and Zhuhai Jinwan Airport—as well as a group of feeder airports, will constitute a cluster that will be developed in two phases. Phase one, due for completion in 2025, will establish a Greater Bay Area airport conglomerate, with greater interaction between the facilities. Phase 2 aims to lift all the airports to a world-class level by 2035 with "safe, green, smart, human and synergetic qualities". Bridges Huangpu Bridge Nansha Bridge Humen Pearl River Bridge Shenzhen-Zhongshan Bridge Hong Kong-Zhuhai-Macau Bridge Rail Urban rail transit (including metros, commuter and regional railways) is expanding very fast. Hong Kong MTR was the first, and its model has subsequently been applied to other networks in the region. The total length of all cities' metro lines is now . Metro Dongguan Rail Transit Foshan Metro Guangzhou Metro Hong Kong Mass Transit Railway Macau Light Rapid Transit Shenzhen Metro Regional and commuter railway CR C-train (several