Walk up School Street from the Downtown Crossing Walgreens and look up at the back of the building at the corner of Province Street, and you'll see these two ox skulls staring back at you.
These bucrania (if there were just one, it would be a bucranium) date to the 1920s, when the building (where the Borders used to be) went up as the headquarters of the Boston Five Cents Savings Bank.
They harken to the days when Boston architects, such as Parker, Thomas & Rice, who designed the bank building, loved embedding Roman, Greek and even the odd Babylonian references in their work (all the buildings with a caduceus? They weren't hospitals, but home to merchants, because Mercury, the god of commerce, had one).
Bucrania, basically ox skulls with garlands, are an old Roman symbol that would decorate temples - at which an ox or two were commonly sacrificed.
Over the decades, the School Street ox skulls have served as the backdrop for other events. Take, for example, this photo of Louise Day Hicks campaigning for mayor on School Street in 1967 (she lost to Kevin White) - look just up above the clock:
You can also find some bucrania carved into a frieze along the exterior of the Municipal Building in Hyde Park's Logan Square.
Hicks/skulls photo from the BPL's Brearly Collection. Posted under this Creative Commons license.