A century ago, Lime Ridge supplied some of the lime and sand needed for California's industrial expansion. Today, surrounded by homes in Concord and Walnut Creek, the area is easy to dismiss as a drive-by experience. However, if you take a walk with people who know the place, you'll learn it's actually a reservoir of rare plants and animals, a laboratory for restoration, and the setting of a triumphant chapter in a local conservation history. The four-mile hike is from 9 a.m.-12 p.m. on Saturday, Jan. 26. RSVP required 947-3535.

Are you receiving Express, our free daily e-mail edition? See a sample and sign-up for Express.