Downtown Phoenix's hottest sports fixture is this immense masterpiece of engineering. Home to the Arizona Diamondbacks, the facility seats more than 48,000 and features a retractable roof that exposes the natural turf to sunlight. During the intense heat of summers here, this air-conditioned ballpark cools down the heated competition. Other highlights of the building include a pool and spa that can be reserved for private parties. Tours are available year-round and last a little more than an hour.