That is the FIJI house (oldest frat at WPI as it dates back to 1891) at the corner of Salisbury and Boynton across from Institute Park. It was a time honored tradition at my alma mater WPI to surreptitiously in the dark of the night paint over their rock emblazoned with their letters which used to be in the park directly in front of it. The photo of the new house shows the rock now situated on its property.
WPI has actually added more greek chapters as its enrollment has more than doubled in the last 30 years (now over 5k undergrads) . There are now thirteen frats and seven sororities. Most of these are still located on or near Boynton, Dean, and Wachusett Streets just east of campus between Highland and Salisbury Streets.