This is a stage. In a cave.
You can see the steps leading up to it on the right hand side of the picture and the stage itself is a flat surface between the two pillars in the centre.
The acoustics are incredible and I imagine the many soloists and vocal groups who have played there sound amazing.
But it wasn’t always a stage. Mostly it was and still is just a cavern in a cave. It took imagination and initiative to see a stage there and make a concert happen.
Some musicians don’t want to invent stages. They want to wait until the old stages open again. There’s nothing wrong with that.
But others are looking for new ways to play, places to play, new stages on which to perform. Maybe this example can help.