As I mentioned earlier (probably several times), I had always enjoyed riding Boston's MTA rapid transit system as a kid in the 1960s. Those "railfan" memories have lasted all my life. So it's no surprise that, once I had access to the tools and the creative process started to gel, I would build a few MTA-related dioramas.
Not long after I started modeling, I got an idea to build a subway trolley station. This was my first diorama not related to my main layout, although it's really just a "mock-up" built rather quickly using mostly from foam core board. I also designed it so that it could sit on my layout, with the tracks running through the station. (This was prior to the town's expansion so there was more room on the table.)
Someday I plan to build a version of this station as a separate, stand-alone diorama connected to my main tracks. (My PCC trolley waits patiently for the expansion.)
By the way, there really is a Fenway station in Boston, but this isn't it. The real Fenway station isn't underground, nor is it near Fenway Park.