Hangzhou (Zhejiang Province), former capital with a famous lake, one of China's top destinations for domestic tourists. Marco Polo wrote of Hangzhou the city is beyond dispute the finest and the noblest in the world.
Nanjing (Jiangsu Province), capital under several dynasties, most recently 1912-1949
Ningbo (Zhejiang Province), a major trading port in the tea clipper era, still an important port and industrial city
Shanghai, China's largest city and greatest economic center; in some ways, the cultural capital as well
Suzhou (Jiangsu Province), old city of canals and gardens, now a major center for high tech. The Chinese have a saying that heaven has paradise but Earth has Hangzhou and Suzhou.
Originally, Hangzhou and Nanjing were the great cities of this region; both have been the capital of China. Suzhou was another important city, famous for its gardens, canals and silk.
In the 19th century, after one of the Opium Wars, China was forced to open certain Treaty Ports to foreign trade. The two in this region were Ningbo, which until then had been mainly the port for Hangzhou, and Shanghai, until then an insignificant town strategically positioned near the mouth of the Yangtze. Both developed rapidly after that. By the early 20th century, Shanghai became one of the world's richest and wildest cities.
As anywhere in China, Mandarin is the lingua franca; nearly everyone can speak it. As elsewhere in China, English is not widespread but some people speak it quite well.
The region does have its own language, called Wu or Shanghainese. This is a populous region and the number of Wu native speakers is large; at 78 million it is rather more than French or Italian. There are local variants of Wu; the standard is that of Suzhou (an older city, capital of the Kingdom of Wu centuries back, and home to many scholars), not that of Shanghai.
Perhaps the commonest way to reach the area is to fly to Shanghai. There are two airports. Pudong is a major international airport with connections all over the world; Hong Qiao handles mainly domestic flights.