Thank you, Google Maps, you gave me my next adventure destination: Tai Tam Reservoir 香港島 大潭水塘. There are at least three sections of the reservoir, and it takes about an hour by MTR and bus from Central Hong Kong.
(Map)
Here’s what it looks like:
And a picture of the bridge, from Percy Tai 漆園童: https://ssl.panoramio.com/photo/66047778
And a family:
The Hong Kong Files 