It’s hard to believe, but Denver International Airport (DIA, 303/342-2000, www.flydenver.com ) is the largest international airport in the country and the third-largest international airport in the world. Denver International Airport opened in 1995 to a combination of fanfare and ridicule (that state-of-the-art baggage system never did work), but its distinctive white-peaked roof has become a symbol of the city—and copied in smaller versions.
The airport is 25 miles from downtown Denver , and like most airports these days it’s a mall of sorts too (look for Tamales by La Casita and Dazbog Coffee). In addition to the shops and restaurants, the airport offers free Wi-Fi (call 800/986-2703 for technical support) and has a U.S. Post Office (Level 6, Jeppesen Terminal, closed Sun.), a USO Center (303/342-6876), and a Jewish and Christian Interfaith Chapel and Islamic Masjid, all open 24 hours per day. Security wait lines can be miserable; try the line leading to Concourse A, then take the elevator to the trains to reach other concourses.
DIA is served by most major domestic airlines; Frontier Airlines (303/371-7000 or 800/432-1359, www.frontierairlines.com ) is based in Denver. Southwest Airlines (800/435-9792, www.southwest.com ) has provided some good low airfare competition, especially since United Airlines’ (800/864-8331, www.united.com ) low-cost carrier, Ted, fizzled and left the market. American Airlines (800/433-7300, www.aa.com ) has many flights daily to and from DIA. International airlines that serve DIA include Air Canada, British Airways, Mexicana, and Lufthansa.
Be sure to note your baggage claim number and location, as there are baggage claim carousels on both sides of the terminal, east and west.
It’s typically a $45 flat rate to take a cab to or from DIA. Bus service is the cheapest transportation at $9 one-way or less for seniors, children, and advance purchases. Shuttle vans are available at the airport to take passengers directly to destinations like Vail , Estes Park, and Boulder  and directly to downtown Denver  hotels. Colorado Mountain Express (970/926-9800 or 800/525-6363, www.ridecme.com ) goes to Vail, Aspen, Keystone, and other ski towns; Estes Park Shuttle (970/586-5151, www.estesparkshuttle.com ) costs $85 round-trip from the airport to Estes Park; Super Shuttle (303/370-1300 or 800/258-3826, www.supershuttle.com ) offers door-to-door service with discounts for ride shares. Contact the airport’s Ground Transportation Information Office (Level 5, Jeppesen Terminal, 303/342-4059, daily 6:30 a.m.–11:30 p.m.) for additional information about services.
There are ten rental car companies based at DIA and each provides free shuttle service to its rental lot. The rental car agencies also have service counters in the Jeppeson Terminal, Level 5.
There is short- and long-term parking at DIA, and even valet parking for $27 per day. The closest garage parking is $18 per day or $2 per hour, and uncovered parking lots that are still walking distance from the terminal cost $9 per day or $1 per hour. The west-side parking lots seem to fill up faster than the east side. There are cheaper parking lots that require shuttle bus service to reach, and those cost $5 per day or $1 per hour.
Light rail trains (RTD, 303/299-6000, www.rtd-denver.com ) that go from suburbs to downtown are packed at peak rush hour times. There are plans to keep expanding the number of lines available, maybe eventually providing service to the airport.
Denver ’s Greyhound Bus Station (1055 19th St., 303/293-6555, www.greyhound.com ) is conveniently located downtown, walking distance from hotels, car rental agencies, local bus depots, and Union Station .
To get around Denver and to and from suburbs and other Front Range cities, use RTD (1600 Blake St., 303/299-6000, www.rtd-denver.com ). The main terminal is in LoDo at 16th and Market Streets, where you can pick up schedules for just about every route. RTD provides bus service to and from the airport, Boulder , and many other towns in the greater metro area. City and regional buses are almost always equipped with bike racks in front.
No matter where you are coming from by car, you’ll end up on I-70 (east–west across the state) or I-25 (north–south across the state) to get to Denver . The most unpredictable part of the drive can be I–70 in the mountains, where icy roads, traffic accidents, and rock- and snowslides have all closed the road at one time or another.
There are major car rental agencies at both the airport and downtown. Downtown you can walk to Avis (1900 Broadway, 303/839-1280, www.avis.com ), Enterprise Rent-A-Car (351 Broadway, 303/575-0044, www.enterprise.com ), and Hertz (2001 Welton St., 303/297-4900, www.hertz.com ).
Like most midsize to large cities, Denver is plagued by gridlock on the highways that circle much of the city. Light rail trains did not do much to alleviate the rush-hour congestion, even though the trains are standing-room-only during rush hour. Fortunately, it is possible to get around the city on foot, bicycle, bus, or light rail, with limited expense and hassle.
Especially when you are doing any winter driving in the mountains, check road conditions first at www.cotrip.com  or www.dot.state.co.us/TravelInfo/CurrentCond/ , or call 303/639-1111 or 877/315-7623.
It’s almost impossible to walk out to the curb of any Denver  street and hail a cab. If you are downtown, go to the entrance of any hotel and there is usually a small fleet of cabs waiting for a fare. Otherwise, you have to call and wait for the taxi to show up.
The most interesting thing to happen with Denver taxis is the transition to hybrid vehicles. Metro Taxi (303/333-3333, www.metrotaxidenver.com ), the city’s largest taxi company, began converting their fleet to hybrid-electric Toyota Prius cars in 2007, and Yellow Cab (303/777-7777, www.yellowtrans.com ) added some hybrid vehicles in 2008. There is also Freedom Cab (303/444-4444, www.freedomcabs.com )—just look for the purple cars.
Denver  is an increasingly friendly city for bicyclists as two-wheeled transportation gets more support as an environmentally friendly alternative to cars. Many city streets have bicycle lanes, biking paths are common, and city and regional buses (say, going to Boulder ) have bike racks on the front so people can pedal to the bus stop, ride, then pedal on home or to the office.
Learn about bicycle ordinances, find bike maps, and get riding tips at www.denvergov.org/Bicycle_Program/ , or check out www.bikedenver.org , a bicycling advocacy group’s blog. The Denver Bicycle Touring Club  organizes group rides for members throughout Denver.
There are five companies that offer wheelchair transportation service from DIA, and elsewhere around Denver , with reservations. RTD’s Access-a-Ride (303/292-6560, www.rtd-denver.com ) is for people who cannot board a wheelchair-equipped bus. Metro and regional RTD buses—including the free shuttles on the 16th Street Mall—are wheelchair accessible.
Both Metro Taxi (303/333-3333, www.metrotaxidenver.com ) and Yellow Cab (303/777-7777, www.yellowtrans.com ) have wheelchair vehicles available for passengers. Dashabout (800/720-3274) offers service from DIA with 2–3 days advance notice; Mobility Transport Services (303/295-3900) requires 24-hour notice.