Picturesque, Downtown Crossing is not, as it is packed with every conceivable kind of discount store and street vendor, but the area hums with activity (of both the low- and high-end variety), and sitting amid all the action is the 22-story Hyatt Regency Boston. Walk out of the crowds and into the cool marble lobby decorated with dark-wood furnishing and geometric-pattern rugs. Take an elevator ride upstairs to a guest room equipped with an iPod dock, pillowtop mattress, and understated earth-color furnishings. Or sweat the day away in the 24-hour fitness center. Smart travelers call ahead for good deals on theater or shopping packages. Bonus: the hotel is fairly green—among other things, it composts leftover food and uses energy-efficient lighting, including motion-detector light switches.