Calistoga, California

Across the country, the Calistoga springs offer similar healing properties, but in a much more developed and luxurious setting. The hotels here tend to have "mineral baths" that are actually swimming pools with mineral spring water piped in; and mud baths safely contained in a custom-designed bath inside the spa. If you prefer luxury over a natural setting, any of the big hot springs spas will suit you, from Calistoga Spa to Solage to Indian Springs.

Lena Katz is the senior travel correspondent for JustLuxe, covering trends, tastemakers, news and more.