Are we in the moon? No just in a village plenty of underground caves in the heart of Ribera del Duero. In the XVI th century when you were thirsty you drand wine and tried not drink water. The water could be contaminated if you were leaving closed to sheeps and cows. So in order to be healthy (and also happy) you drunk wine instead of water any time. But at that time. Before learning how to age wine in oak barrels, the only way to keep young wine not aged in barrels was to keep it in underground caves with cool and constant temperature, no light, no sound. That you could only get it by digging and having ungerground caves. The chimneys were to provide the underground caves of ventilation that ensured that the air in the cave was breathable and cool. If you have not been yet in such underground caves you have another experience to live.