Visit the industrial legacy of the Bay Area amid a lush redwood forest north of Santa Cruz. There's not much left of the 19th century lime processing industry of the San Francisco Bay Area. Processing lime -- a key ingredient in plaster and mortar -- was big business in the California boom years after the Gold Rush. New technology (namely Portland cement) made lime obsolete early in the 20th century, leaving the uncanny recuperative powers of the coast redwood to reclaim the forest where factories once stood. The decaying lime kilns at Fall Creek Unit of Henry Cowell Redwoods State Park are about all that remains of the local industry. This hike lets you explore the old kilns up close. It's mostly rusting junk now, but the hike to it -- along the burbling waters of Fall Creek -- is one of the prettiest in the Bay Area. Best times to go: This is a true four-season park; just bear in mind it can be quite cold in the morning.