While trains intermittently rumble past and small planes occasionally scream overhead, the Corson Building (c. 1910) sits behind its wisteria-and-rose-covered wrought-iron fence, an island of loveliness marooned in Georgetown’s grit. Inside, everything’s picturesquely rustic and seating is communal. Matt Dillon’s reverence for the local and the seasonal is everywhere in evidence here. Corson is open Thursday through Sunday for dinner service, and dinner here is always a special occasion.