Well, if I can step outside the strictly megalithic arena for a while, then it’ll be the rock garden of Ryoan-ji, set in the western mountains of Kyoto.
I first visited Ryoan-ji back in the mid 60s, and then countless times since (one of those places that always draws you back - and we all have a least one of those :-) You can’t actually walk in the rock garden itself (the monks carefully rake the sand into a pattern each morning) but you can sit on the temple’s wooden veranda which is just and arms-length away.
Lived in a little hut, just a few minutes from Ryoan-ji, for about a year so it was a place I could visit anytime. Though you have to pay to enter the temple itself and view the rock garden, the larger garden (which surrounds the temple) has a lotus lake and is free to walk around. There’s even a little tofu restaurant overlooking the lake. As you walk up the stone path to the door, one of those bamboo features that fills with water and then CLUNKS onto a stone as it tips itself empty greets you.
Wrote about Ryoan-ji on TMA some time ago, but there’s a photo of the rock garden here for those interested.