One room of the cave, wrapped around you, played by voice. Speech is recognised inside the headset — nothing is sent anywhere. The first visit downloads about 46 MB and then caches it.
In VR: hold the trigger to speak · grip grabs the reading panel so you can put it where you like · X or Y on the left controller opens the menu · thumbstick scrolls it, or sideways resizes it. Panel shape, size, position and push-to-talk are all remembered.