The Taj (address and info)
This is a tough one. The area is replete with gems (I mean, the Saks' bathroom has a freakin’ lounge chair). But the Taj bathroom, inside the city’s original Ritz-Carlton, is just old-timey glorious. This isn’t a bathroom; it’s a bona-fide powder room, harkening back to a day when going to the restroom was a more genteel affair.
Runner-up: Four Seasons & L’Espalier (tie)
KO at the Shipyard (address and info)
It’s about the journey, not the destination. Specifically, the graffitied wall directions that point you upstairs, along with many variations on the word "bathroom": potty, baños, toilet, and loo, to name but four. And once you get there, the destination has more terrific reading material (translation: anti-alcoholism ads in Russian). Did we mention the view of the Boston Harbor? It may rival the scatalogical Soviet propaganda.