Working out while traveling is important in order to fight jet leg and to feel well both mentally and physically. There is a way to work out in most every location, even on the plane. On long flights, you could take some laps around the plane and do some stretches. If you are strategic with utilizing your space, you can even do sit-ups. If you are gym person and your hotel does not have a gym, check out the local gyms online. Some gyms offer a free trial or reduced fee trials. For example, Crunch Fitness in DC offers a free guest pass on their website. Or, if you are staying longer in DC, Washington Sports Clubs offer a 30 day trial membership for as low as $30. You can save money, workout, and explore the town by running/jogging the neighborhood. Matt and I do this every single morning when we are traveling. We run different streets to find out where we would like to explore later on in the day. Additionally, fitness travel is becoming more popular (Google: “fitness travel”). You can find groups online that are traveling the world with their bikes, by running, or just by being active daily during their vacation. Finally, you do not need to do a formal workout if you have active activities during the day. For example, on the road I have biked the Golden Gate Bridge, jumped on large dominoes in Philadelphia, sandboarded in New Zealand, climbed a large rock in Texas, 4wheeled in Belize, swam in the ocean in Tahiti, walked across the Brooklyn Bridge, golfed at the Chelsea Pier, and fished in Colorado (see photos below). All in all, staying active during your holiday will allow for you to come home and not only feel more relaxed, but feel better about yourself and all the food you got to eat. 
Those are great suggestions, on a subject my husband and I have been talking about a lot lately. Thanks!