The video shows the updated Rock Henge, an image of the original is below.
Rock Henge is obviously modeled after Stone Henge, a rl thing, modeled by people who understood geometry, that's right, Mathletes! Rock Henge is not that mathematical, so leave your protractor at home.
Dancing with NPCs is a part of the Aine Caoimhe's dance systems: Paramour -> at Rock Henge, we took it one step further by using the (Aine) avatar cloning system and adding a dance crowd - they show up when you show up - never dance with one NPC when you can dance with 10. :)
hop://login.greatcanadiangrid.ca:8002/Silver Birch/338/166/25 is where you'll find it.