If you have a long layover, you may be thinking about leaving the aiport for a short excursion! If you are, consider just how much time you have, where you are, and how much time it will take to get to and from the airport.
You will have to go through security again and you may also have to collect and re-check your bags. If you're in a foreign country, you will have to pass through customs and you may need a visa to leave the airport and entry the country.