It depends on your circumstances - and belongings. Are you coming in on an international flight and need to go through Immigration?

Is your luggage checked all the way through - or do you need to pick it up and go through customs - or just check it again into an ongoing flight?

And what is your ongoing flight - how early do you have to check in for that?

Logan is very close to downtown and you can ump in a cab and be there in 20 to 30 minutes no problem.

But how much time do you really have between flights?

If you have a couple of hours and just want to enjoy a jaunt, you can take the shuttle bus to the water taxi and go to Rowe's Wharf. The views of the city are gorgeous and it is about a fifteen minute ride. You can have a drink on the terrace at Rowe's Wharf and watch the boats come and go or you can walk down the waterfront to Christopher Columbus Park and into the North End, where you can at least walk past Paul Revere's house and into Christ Church, where they raised the signals to send Paul Revere on his ride. Stop for a quick meal?

From the North End, you can walk to Quincy Market and Faneuil Hall, then to the Old State House, site of the government when Massachusetts was a colony. It was also the site of the Boston Massacre. All these are on the Freedom Trail, marked by a red line on the sidewalk.

Handily, there is a Blue Line subway (T) station in the basement of the Old State House, and it takes you right to the airport station, where you get a shuttle to your terminal.

What do you do with your luggage while you do this? If it isn't checked through, you can check it for your next flight, though I wouldn't mention that you are leaving the airport. Or you can check it with the bellman at the Hyatt hotel which is right next door to the ferry stop. In fact, you can take their shuttle or the ferry shuttle, whichever comes first.