The soul cave house is wonderful. We only stayed in this property for two nights, but they were a relaxing, cozy, and "I can't get enough of this view" two nights. Seriously, the view is breathtaking...there is even a little platform up a few steps that is great for a perfect panoramic shot of the caldera. I put a chair up there each night to enjoy the breeze and take in the view. Just one note - the cave house is conveniently located near the main walking avenue and is paired with a great view, so expect tourists to walk along the path in front of the property relatively frequently.
The cave house itself is quaint and cozy, and the shower/bathroom is small but very nice. Staying in any of Maria's properties is recommended...you'll have wifi, a refrigerator with a bottle of water, some maid service (new towels, bathroom cleanup, etc), and Maria herself is a great host.
If you book a stay in the soul cave house, you are guaranteed to have a fantastic and memorable time.