Phú Yên Province
The Cả pass (Đèo Cả) is a mountain pass in Phú Yên Province, Vietnam. The mountains are known as the Cả pass mountains (núi Cả Đèo). Historically the Cả Pass was the second most difficult col in Vietnam after Hải Vân Pass. In 1611, the Nguyen pushed their border down to Cả Pass.