The Royal Observatory, Greenwich, London founded in 1675. The site of the Prime Meridian as well as the origin of Greenwich Mean Time, now the Observatory's historic buildings house a museum of astronomy, navigation and timekeeping as well as the Weller Galleries of modern astronomy and the award winning Peter Harrison Planetarium.
The Temperate House - Kew Gardens. This is the largest surviving Victorian glasshouse in the world (b. 1859). It's also the final resting place for many plants which have outgrown their initial berth. The Chilean Wine Palm is 18 metres tall, & was raised from a seed 20 years before the Temperate House was built. Royal Botanic Gardens, Kew, TW9. Nearest Tube: Kew Gardens.