Infernal Affairs - Andy Lau (2002) - Chai Wan North No.2 Fresh Water Service Reservoir, Chai Wan

The final grave scenes in the movie almost look as though they were shot on the roof of a building with some astroturf laid down, but it turns out that the grass is real and belongs to the Chai Wan North No.2 Fresh Water Service Reservoir which sits on the north slope of Sai Wan hill (the same hill that has the battery at the top and the not-so-long ago mentioned Lei Yue Mun Holiday Park). It's possibly a popular filming spot because it has its own entry on the film services office website.