Shanhaiguan is the eastern terminus of the Great Wall, where the fortifications march down from the mountains and plunge straight into the Bohai Sea at a spot called Old Dragon's Head. The walled town itself, with its massive east gate inscribed First Pass Under Heaven, was one of the most strategically important fortresses in Chinese history — the pass between the mountains and the sea that controlled access to the northeastern plains.
The town is compact and can be walked in an afternoon. The restored city walls are impressive, and the stretch of Great Wall climbing into the Yanshan Mountains behind the town at Jiao Mountain offers good hiking with far fewer crowds than the sections near Beijing. The Great Wall Museum gives essential context, and the legendary Mengjiangnü Temple — a folk shrine to the woman whose tears, in the old story, brought down a section of the wall — sits east of town. Shanhaiguan is easily reached by train from Beijing (about two hours by high-speed rail) or as a side trip from the nearby beach resort of Beidaihe.