Lost a crossword puzzle

I guess it should be: the sea

Is the answer really embarrassing?

the Chen Dynasty

[~ Stone] A. Place name, in Haining County, Zhejiang Province, China; B. Ancient place names, in the west of Mengjin County, Henan Province, China; C Mountain name, one in the northwest of Shouxian County, Anhui Province, China, and the other in the east of Haining County, Zhejiang Province, China.

The ancient "canyon" is a valley between two mountains.