The largest of the Náchod-area fortifications is the artillery fortress at Dobrošov, about 5 km south of town on a forested hilltop. It was meant to be the linchpin of this stretch of the defensive line — three completed infantry blockhouses linked by a network of underground galleries, with three more artillery casemates planned but never built when the line was abandoned in 1938.
Guided tours descend into the subterranean passages, which are cold even in summer (bring a jacket). The site is normally open May to September with a Monday closing day; check the current schedule before driving up. The walk through the woods to the lookout tower above the fortress is worthwhile on its own.