With the opening of the bridge, the Pearl River Delta becomes one of the dramatic megalopolis in the world. It links the Chinese megapolis of Guangzhou, Foshan, Jiangmen, Zhongshan, Zhuhaï (China) to Macau and Hong Kong. This region of China is populated by more than 120 millions of people.
See this article from South Morning China (Hong Kong): https://www.scmp.com/news/hong-kong/politics/article/2169893/first-cars-and-buses-begin-crossing-pearl-river-delta-hong
The beginning of the bridge in Hong Kong last July. It links Hong Kong and Macau-two Chinese territories which have a different political and economical system than the rest of China- and Zhuhaï, the fast growing city beyond the Macau border. The total lenght of the bridge is 55 kilometers, which is the largest bridge in the world.
With the bridge, time to travel from Hong Kong to Zhuhaï (the Chinese town bordering Macau) is reduced from 1h10mn by boat to 40 minutes. The bridge also connects Hong Kong to Macau in 35 minutes (1 hours by boat).
The territory of Hong Kong has a lot of islands (with very different density of population) which are well-connected with long bridges.
In Macau, the original island was only 26km2. In the south, the small islands of Taipa, Cotai and Coloane have been enlarged and linked to Macau by a impressive network of bridges. Macau has one of the most important density of population in the world (more than 22 000 inhabitants per km2.).
The bridge which links Macau to Taipa island.