This free visitor centre provides insight into the military installations scattered in the surrounding hillside. The 202nd Batteria Chiappa guarded the coast during the Second World War, and you can still poke around the various bunkers, sentinel posts, barracks and armoury (pick up a map to see the layout). The visitor centre runs one-hour guided tours of the military post.
It also offers longer tours of other parts of the island, which you'll need to book in advance (these depart from San Rocco, and cost €100 per group for a half day).
You can get there on foot along the scenic trail from Camogli (about a 90-minute walk via San Rocco) or take a ferry to Punta Chiappa and hike up from there – it's a short but steep climb that ascends 250m (around 30 minutes).