2. The famous Xiongguan is:
(1) Jiayuguan, known as the first male pass in the world, is the only pass of the ancient Silk Road.
(2) Shanhaiguan, known as the first pass in the world, echoes Jiayuguan from a distance.
(3) Yanmenguan, known as the first pass in China, is a battleground for military strategists in past dynasties.