R V.
Yelp
If you've been dying for an excuse to check out one of those lavish historic homes on Beacon Hill, give this one a try. The tour is inexpensive ($5) and the house is gorgeous, with period furnishings mixed in with modern recreations. I would presume that the tour groups are typically small because it's not one of those "must-see" locations. Even so, it's right next to the Common (across from the Frog Pond), just a couple hundred feet from the State House so the location is very easy to find. Take the T to Park Street, for example, or park in the garage under the Common.
The tour itself was led by a very friendly guide. Most of the tour seemed to focus on architecture or, more specifically, how the home changed over the years. I was not entirely interested; what usually drives me to visit a historic house is the person (or people) connected to it. In this case, I heard very little about William Hickling Prescott (a well-respected historian who was nearly blind) - up until the end. Inexplicably, there also was a focus on the American Revolution and how Boston was made up of landfill (neither aspects were relevant to this house). My guess is they were catering to the out-of-towners.
Ultimately, I wouldn't call the Prescott House a hidden gem. But, it's worth a visit for folks that don't mind taking a few steps off the Freedom Trail (after all, there's more to Boston than a red line).