“Wine caves require a specific set of geological conditions to exist, the most critical being rock type. Soft enough to excavate, hard enough to remain self-supporting once it’s been carved out. That’s why materials like volcanic tuff fit the profile, which is what you find in Napa Valley. The famous California wine region sits in a zone of ancient volcanic activity, with hills on either side of the valley that are made up of volcanic rock. The first Napa caves were dug in the late 1800s by wineries like Schramsberg and Beringer (both of which you can still visit for a tasting).”
