Lung Tsai Ng Yuen (龍仔悟園) is surely one of the most surprising places in Hong Kong's countryside - a Chinese landscaped garden set in the hills of southwest Lantau Island, accessible only by hiking. I've read that it was developed and planted with ornamental trees by the late Mr Woo Quen-sung (this info from Hong Kong Country Parks, by Stella Thrower). Also known as Ng Yuen Garden, it's within the Man Cheung Po SSSI (Site of Special Scientific Interest).
Though the buildings and zigzag bridge over the carp pond are ageing, Mr Woo's descendants evidently maintain the garden. But, sadly, it's usually closed to the public - though you can enjoy the above view from the dam used to create the pond (signs warn this dam is unsafe; maybe some day it will crumble).
Recently, I was lucky enough to arrive and find the garden was open - so took the chance to wander around, and take photos.