Bay seniors looking for a less strenuous caving activity should consider a visit to the volcanic rock caverns at Schramsberg Vineyards in Calistoga. Built in the 19th century by Chinese workers it’s a 2-mile,75-minute trek lit by candelabras and lined with 2.7 million bottles of chardonnay and pinot noir based sparkling wines. Learn all about their celebrated methode champenoise. Belly up to a bar for tastings. It’s all very Phantom of the Opera.