Hong Kong Museum of Coastal Defence (Defense)

 Located on Hong Kong Island at the far east end, this museum traces the history of Hong Kong's maritime protection. It's converted from the old Lei Yue Mun Fort, high on a hill.

 After buying your ticket, an elevator brings you to the top (the structure seen in the first picture), where it's a short stroll a bit more uphill to get to the redoubt, where the main exhibits are held. Along the way you'll see some existing structures.

 Almost every old battery and other structure remaining is accessible and explorable, unless it's just unsafe.

 You can go inside the storage areas, and walk out and see the view from where the cannons once sat.

 A small town across the water makes for a nice view now.

 The redoubt has been modernized, in that it is covered with a nice roof and a second floor and air conditioned. The basic structure remains, though.

 Hong Kong is still a major shipping port, and the occasional views of the waterway afford the opportunity to see barges moving in and out.

 You can "explore" one of the guns near the redoubt (seen in a picture above). The old leather pouch remains as well as instructions and engravings for setting the gun.

 Inside the main structure, the old passageways around the outside hold a permanent exhibition outlining the 600-year history of maritime defense.

 All of the rooms are accessible from the central area, now covered.

 The forts were used through World War II, when new fighting techniques rendered them obsolete.

 A series of tunnels leads out and around the grounds, allowing access to the batteries.

 You can go both inside and outside the batteries.

 Some exhibits can be found outside, including this "opened up" torpedo.

 The gun mount is visible in at least one place.

 Continuing with the exhibits inside, mannequins and artifacts help tell more recent stories, including the Japanese occupation during Word War II.

 Old books always fascinate me.

 The second, modern floor of the redoubt has lots of open space, but I didn't see anything up there that interested me as a solo visitor. There is a restaurant/cafe of sorts near the redoubt but not inside.

 After visiting the redoubt, it's a good idea to follow the route down the hill where the other old structures remain.

 Some areas are off limits for obvious reasons.

 One particular trail leads down to the water and the torpedo room. There, you'll learn about how the torpedoes were stored and how they would have been launched.

 All of the old buildings look like they'd be really cool little places to live. I'd totally live in here!

 One of them even has a skylight!

 Back towards the bottom, one of the ruins has a collection of monuments.

 This building was built right into the mountain and stored ammunition far from everything else for safety purposes.

 The monuments come from around the world.

The museum is open at 10AM (closed Thursdays), closing at 5PM or 6PM depending on the time of year. Admission is only HK$10. Access is easy from Shau Kei Wan MTR Station, though it is about a 15 minute walk. The museum's website has all the details you'll need.