Alright, I think most people have heard of Beijing, Shanghai, and Hong Kong. And you probably guessed they are major economic powerhouses. Well, pretty much all the other major cities in China you never heard of are also economic powerhouses that have outputs compared to entire countries.

Rank	城市	Chinese City	City GDP (2015, PPP)	Comparable Country
#1	上海	Shanghai	$810 billion	Philippines
#2	北京	Beijing	$664 billion	U.A.E.
#3	廣州	Guangzhou	$524 billion	Switzerland
#4	深圳	Shenzhen	$491 billion	Sweden
#5	天津	Tianjin	$478 billion	Romania
#6	蘇州	Suzhou	$440 billion	Austria
#7	重慶	Chongqing	$425 billion	Chile
#8	香港	Hong Kong	$414 billion	Peru
#9	武漢	Wuhan	$324 billion	Israel
#10	成都	Chengdu	$306 billion	Norway
#11	杭州	Hangzhou	$275 billion	Greece
#12	南京	Nanjing	$272 billion	Denmark
#13	無錫	Wuxi	$270 billion	Morocco
#14	青島	Qingdao	$266 billion	Hungary
#15	長沙	Changsha	$246 billion	Sri Lanka
#16	大連	Dalian	$245 billion	Finland
#17	佛山	Foshan	$235 billion	Uzbekistan
#18	寧波	Ningbo	$233 billion	Angola
#19	瀋陽	Shenyang	$230 billion	Sudan
#20	鄭州	Zhengzhou	$210 billion	Ecuador
#21	唐山	Tangshan	$191 billion	New Zealand
#22	東莞	Dongguan	$186 billion	Ethiopia
#23	煙臺	Yantai	$184 billion	Belarus
#24	濟南	Jinan	$174 billion	Azerbaijan
#25	南通	Nantong	$170 billion	Slovakia
#26	長春	Changchun	$163 billion	Dominican Republic
#27	西安	Xi'an	$161 billion	Kenya
#28	福州	Fuzhou	$160 billion	Tanzania
#29	哈爾濱	Harbin	$159 billion	Bulgaria
#30	合肥	Hefei	$157 billion	Tunisia
#31	石家莊	Shijiazhuang	$156 billion	Guatemala
#32	徐州	Xuzhou	$150 billion	Ghana
#33	常州	Changzhou	$147 billion	Serbia
#34	溫州	Wenzhou	$131 billion	Croatia
#35	淄博	Zibo	$123 billion	Panama

What is even more amazing is that these cities don’t exist in isolation. As per urban-planning doctrine in China, cities are interconnected in larger metropolis regions. The three main metropolis regions of China correspond with the Chinese cities you've heard of:

Yangtze River Delta (長江三角洲)

With a combined GDP of $2.17 trillion, which is comparable to Italy, the Yangtze River Delta contains cities like Shanghai (上海), Suzhou (蘇州), Hangzhou (杭州), Wuxi (無錫), Ningbo (寧波), and Changzhou (常州).

Pearl River Delta (珠江三角洲)

With a combined GDP of $1.89 trillion, which is comparable to South Korea, the Pearl River Delta has cities like Hong Kong (香港), Guangzhou (廣州), Shenzhen (深圳), Foshan (佛山), Dongguan (東莞), and Macao (澳門).

Jing-Jin-Ji (京津冀城市群)

With a combined GDP of $1.14 trillion, which is comparable to Australia, Jing-Jin-Ji holds the two largest cities in northern China, Beijing (北京) and Tianjin (天津), as well as Baoding (保定), Shijiazhuang (石家莊), Tangshan (唐山), Cangzhou (滄州), Langfang (廊坊), Zhangjiakou (張家口), Chengde (承德), Qinhuangdao (秦皇島), and the planned Xiong'an New Area (雄安新區). The name is derived from the second characters of Beijing and Tianjin and the single-character representation of Hebei Province, named for the historic Ji Province (冀州)