If you need a break from the city life, Nan Lian Garden is not too far away. Located in Diamond Hill Kowloon, it's a large garden that changes with the seasons, and spreads wide over a fair amount of space, especially compared to the dense, cramped city life.
Stop by and appreciate the enormous koi pond, probably the largest one I've seen in my life, then stop by for lunch and afternoon tea at the restaurant behind the waterfalls. The garden was a collaboration between the neighboring Chi Lin Nunnery and the Hong Kong government. Be sure to visit the nunnery as well, with its bonsai displays, lotus ponds, and intricate, traditional Buddhist halls.