An exclusive club at night.
The door on the side opens, and inside is a stage, a bar, and gambling tables come out for all to bet their trading goodies away.

I had a great experience getting to this. It's one or two miles north of Black Rock City, and in cycling there I thought I saw this illuminated in the distance, but it turned out to be the moon rising. THE MOON? But it seemed below the horizon! That because the area is so flat that the slight curve of the Earth is experienced, and as I'm about 6 ft tall, my height can see over the slight curve, and I could see the moon "below" the horizon.
But what it really is, that the horizon is below eye level, but at night you believe the horizon is AT eye level - it isn't!