Open Top Sightseeing is a great way to orient yourself in the city, perfect for first-time visitors. You can get on and off throughout the tour, and your ticket is good for two days. This allows you to stop and go to a Smithsonian Museum, or the White House, or have lunch in Dupont Circle or in Georgetown, and get back on. The double-decker buses also stop at several hotels, so you can use this as your chief method of transport for a couple of days. The narrative is interesting the first time, but if you know the city, or are repeating part of the trip, you may find yourself tuning out when the driver tells a story you've already heard.
Bike the Sites is the Washington, D.C., version of the national company, Bike and Roll. There are three daily tours: Capital Sites Tour, Monuments Tour, and summer only, both at night. The three-hour tours are all easy and great for families, though you may not want to take young kids who aren't great riders (and need to go to bed) cycling at night. The Capital Sites tour takes you to the National Mall, Capitol, World War II Memorial and Washington Monument, among other highlights, and you get a little time to wander each area. You don't get a comprehensive tour, of course, but the brief overview lets you figure out where you want to return, and where each place is in relation to other sites. The Monuments tour includes the Vietnam and Lincoln memorials.
The bikes are in very good condition and are adjusted to fit; helmets, water and energy bars are provided. At night, you get reflective vests and lights.
Two-hour Capital Segway tours on Segway personal transporters take you past the White House, Washington Monument, FBI Building and Botanical Gardens, among the 25 attractions. You wear a headset while riding so the tour guide can offer interesting tidbits about the city. Before the tour, you get a brief lesson in how to steer (by shifting your body weight). Note that kids under 16 and pregnant women are not allowed to use Segways.
DC Ducks is a hybrid tour, on land and in water, with an amphibious WWII vehicle. The hour-and-a-half tour is best for families with young children, who love the rather cheesy guides and like making quacking sounds. Kids are usually thrilled by the splashdown when driven into the Potomac River. You go past the National Mall and the famous monuments, but you don't really see that much.
Potomac Riverboat Co. offers narrated cruises on the Potomac River, leaving from Georgetown (or Alexandria, Va.). You go by the monuments and memorials and the JFK Center for the Arts.
These tours do not operate in winter.
