Boards
Gardens of castles/houses/stately homes
Love 'em.
*Really* love them actually, to the point that if I'm on holiday and there are any nearby I will without question go and find them.
Best to date: Monet's garden, which was a bit scruffy but pretty brilliant - I heartily recommend it, if just to go to see the (some) waterlillies.
Now you. Where in the world are the best gardens?