I have a six hour layover in Chicago the weekend before Christmas. What are the three things I absolutely MUST do that I can get done and back to the airport in time?

Long layovers offer a kind of two-for-one deal. If you leave the airport, they offer the chance to explore an extra country along the way, possibly one you’d never thought to visit. But without knowing up front what you’ll have to deal with and careful planning, you could end up missing your flight and your intended destination.

Do I Need A Visa? You will have to check ahead of time to see if you’ll need a visa to enter the destination that you’re arriving at. Check with your country to see what your entry requirement is into your layover country.

Some require visas, even for very short visits, while others don’t. In addition, at certain countries you can pay for the visa when you arrive, but many destinations need to be planned ahead of arrival. For a quick reference, check our widget (right hand side of the website) for to see if you’d need to apply for a visa and for more in-depth information on How To Get A Travel Visa, click here.

No matter whether your flight is domestic or international, you’ll likely receive boarding passes for all legs of your journey at your first check-in, assuming you booked the entire flight at one time and through the same airline (or possibly even a partner airline). If you used a booking engine (i.e. , Travelocity, Expedia, etc.) or your second flight isn’t operated by the same airline or its official partner, you may need to get your second boarding pass at the airline counter operating your second flight.

Either way, allow plenty of time to get to your second gate. At large airports, it can take a hefty chunk of time to get to one end from the other, and may require shuttles—and time finding the shuttles. Generally your luggage will be checked to your final destination on domestic flights, and you can always check with your airline to see if you can check your luggage through to your final destination on international flights.

Many lengthy layovers up to 24 hours are considered a connection, so often times you can check your baggage all the way through on these flights as well. However, on many international flights — including those back into the U.S. or Canada — you may need to collect your luggage and re-check it. If you need to pick up or hold onto your luggage during your layover, you can always leave it in the airport at a locker or Left Luggage facility.

You can find out where these facilities are at the airport’s website, or on our individual airport Layover Guides. If the airport does not offer storage for luggage, you can always leave them in a hotel room while you explore the city. Transit travelers are those not staying in the country or even leaving the airport.

If there’s a “transit” area, you can head there and won’t have to go through customs. Some countries require visas of even transit travelers, so it’s best to check any visa requirements before visiting a country, even if you’re never leaving the airport. For most layovers, you can leave the transit area (and airport) in between flights, as long as you have a visa (if necessary) and go through customs and immigration on the way out, and of course you’ll have to pass through security again on your way back into the airport.

However, some tickets may not permit you to leave the airport. Always check beforehand with your airline to see if your ticket allows you to leave the transit area. Take into account that for many countries, you will have to go through Customs and Immigration upon your first point of entry into a new country, regardless of whether you’re connecting.

Always budget extra time for this when deciding if you are going to leave the airport for your layover. Unless you have to go to a different gate that’s outside the hub where your first flight arrives, domestic travelers are unlikely to have to go through security again. International travelers, though, most likely will have to pass security measures a second time.

About 30 years ago, most of the countries of the European Union, as well as a couple of additional countries, formed the Schengen Area to allow citizens and others to cross borders effortlessly, including for work, travel and living. What this means for travelers from the U.S. is that while you’ll need to go through border control at your first entry into the region, you won’t need to if you’re traveling on to another country encompassed by the Schengen Area. Always check with the information desk about the best, or Layover Guide’s individual guide to each airport, to find the most reliable transportation option for leaving the airport and traveling around the city.

If you are not familiar with the area, or the language, budget for plenty of extra time to get back to the airport, in case of delays or navigational errors. Also, take into account traffic, and distance when computing the time that you have to see the sights.