They paved paradise and put up a Storrow ramp
Nowadays, Charlesgate mostly brings to mind the crumbling ramp system connecting Storrow Drive and the roads of the Fenway - its underside a transient homeless camp next to a mucky "pond."
But once it was a bucolic connection between the Muddy and the Charles rivers, part of Olmsted's creative plan for both creating a key part of the Emerald Necklace and flushing out the Muddy.
Compare the above photo, from the Library of Congress's collection, and taken sometime between 1890 and 1901, to this Google Street View. The only thing the two have in common is the still standing residential building.