From Dave Brigham:
I would love to get inside this place. Built in 1856 by inventor and manufacturer Enoch Robinson, the Round House in Somerville, Mass., is a wonderful oddity shoe-horned into a tight neighborhood in the most densely packed city in New England. It has 14 rooms, is 40 feet in diameter and is on Preservation MASS's list of Endangered Historic Resources, according to this Wikipedia article.
I forget where I first heard or read about this place, but I finally checked it out last week. I was initially somewhat underwhelmed, as I had expected a larger lot, although I doubt any such thing exists in Somerville. I wanted the house to stick out like a beautiful sore thumb, with spotlights shining and signs pointing.
The house sits, somehow, almost unassumingly behind a chain link fence, surrounded on all sides by more typical homes. As I walked around it, trying to get the best angle for a photo, I began to realize how cool the house is. There are numerous great details around the windows and roof lines. I'm not sure what the metal box-like features are on the lower roof.
Located on Spring Hill, not too far from where I lived back in the mid-'90s, the Round House has been under renovation for quite some time. The house evidently had been abandoned for quite some time, according to Wikipedia, before its 2007 purchase by a man who owns a general contracting firm.
Per this 2006 online thread about the house, the owner "intends to restore every significant architectural detail of the house, both inside and outside, over time, and when it is prudent he will move his own family into it, returning the unique structure to its original use as a single-family home." This seems to indicate the house had been broken up into apartments as some point.
For more information about the Round House, including one photo of the interior, and some diagrams and photos showing how rough it looked before the renovation, check out this Centers & Squares realty web site. Also see the photos and research that the late, lamented Creepy-chusetts, Strange-chusetts blog did in 2010.