On this site on June 2, 1875 something happened for the first time. This occurrence changed the course of human history and ushered in the information age.
Once you have finished reading the plaque that details the event, change your course to due South. On this bearing you will see an ancient relic that was spawned from the historical incident. The cache is hidden there.
This is one of the busiest spots in Boston, so use the utmost stealth!
Congrats to Ritell for FTF!!!!
April 25 Update: the container has been replaced and I upped the difficulty due to new CC and the amount of pedestrian traffic.