Gapgotdondae Fortification was built in 1679 to help protect the Ganghwa Straits from invasion. Eight cannons that were set up at the time of construction are displayed onsite. A strategic location from Goryeo onward, the straits have endured multiple invasions and battles over the centuries: Manchu China (13c and 17c), Japan (16c and 19c), France and America (19th century), and most recently the Korean War (20c). Even today, the euphemistically-named Ganghwa Peace Observatory marks an observation point that overlooks and reinforces the armed border to the North.