The botanical gardens in the centre of Lisbon is a tranquil haven from the bustle of Lisbon's streets. Although somewhat run down, the entrance fee is ridiculously cheap: just 1.80€ or for more frequent visits an investment of 8.50€ will provide you with an annual family card.
Anyway spent a quiet 40 minutes or so in the gardens late on Wednesday in the warm late February sunshine mainly watching a duck on a small pond swimming around and cleaning himself.