Weiyuan Fort guarded the Humen narrows, where the Pearl River opens toward the sea. The surviving batteries and walls are a blunt reminder that the Opium War was fought here as a coastal conflict, with foreign ships pushing up the river toward Canton.
The fort is best visited after the Lin Zexu museum, when the geography makes more sense. From the gun platforms you can read the waterway as a military choke point rather than just another industrial river mouth.