Edinburgh's Royal Botanic Garden is the second-oldest institution of its kind in Britain (after Oxford), and one of the most respected in the world. Founded near Holyrood in 1670 and moved to its present location in 1823, its 70 beautifully landscaped acres include splendid Victorian glasshouses (admission £6.50), colourful swaths of rhododendrons and azaleas, and a world-famous rock garden. There's a second entrance to the gardens at 20a Inverleith Row.
The John Hope Gateway visitor centre is housed in a striking, environmentally friendly building overlooking the main entrance on Arboretum Pl, and has exhibitions on biodiversity, climate change and sustainable development, as well as displays of rare plants from the institution's collection and a specially created biodiversity garden.