I should apologize to Kew Gardens that I ever associated it with The Avengers movie (not that one -- the other one you've tried to forget); apparently filming was done at nearby Syon House. Now that I have disassociated the fine Kew greenhouses and grounds with any ridiculous plots to control the world's weather, I can look back at my visit to the gardens with newly-appreciated gravitas. And, in all seriousness, I fully enjoyed my visit to the gardens in the spring of 2009. The gardens claim to have the largest and most diverse botanical collection in the world, and these are on fine display throughout the grounds. I arrived in April, just in time to see great swaths of bluebells showcased throughout the woods. Cherry blossoms and other flowering trees were also in bloom. Within the greenhouses were orchids, water lilies, and a range of plants from alpine to desert climates. I particularly appreciated the engineering of the vast Palm House, with its wide array of palm trees on display. I enjoy wandering around gardens in my travels, and Kew Gardens is among the best I have visited.
Logistics: Kew Gardens, west of central London, is easily accessible by the Underground via the Kew Gardens station on the District Line. There is also bus and train access, as well as a car park for drivers.