Stewart Mineral Springs is one of the most unusual health spas in California, rich with lore and legends. Above cold-water springs that Native Americans valued for their healing powers, the place is deliberately primitive, with as few intrusions from the urban world as possible. Don't expect anything approaching a European spa or big-city luxury here. Designed in a somewhat haphazard compound of about a dozen buildings, 4 miles west of a town called Weed, it occupies a 37-acre site of sloping, forested land accented with ponds, gazebos, and decorative bridges. The grounds are riddled with hiking and nature trails, freshwater streams, and a swimming hole.