Arizona's Organ Pipe Cactus National Monument boasts Sonoran Desert flora and fauna, interesting geology, traces of the historic Camino del Diablo trail, gorgeous scenery, and more.

Most teachers would be happy to keep their students as far away from scorpions as possible. But not Cameron Elementary School teacher Sheryl Marino.

Mike Keller has studied Yellowstone’s thermal features and volcanic underworld since high school, and when he’s not busy directing operations for the park’s concessioner, he spends most of his free time geyser gazing. As the president of the Geyser Observation and Study Association, Mr. Keller possesses both an extreme passion and an extensive knowledge about all things geothermal.