There is not much more to add to the other reviews about Kew Gardens - it makes for a very nice half-day excursion from the hustle and bustle of central London (after a while you even forget the planes flying directly overhead). Even if you are not that much into plants and horticulture, this is the one botanic garden in the world that you shouldn't miss. I went there on a warm and pleasant summer afternoon, and it was really nice to take a leisurely stroll through the garden and see the various greenhouses and other attractions. My highlight was the Princess of Wales Conservatory, which includes 10 climate zones from around the world. I also liked the huge Palm House, the Waterlily House, the Alpine House, the Japanese Garden, and the former royal palace with the Queen's Garden. Before leaving, I also enjoyed the views from the Treetop Walkway, 18 metres above ground (even though I cheated and took the lift to reach it...).