A room within Kirkland House at Harvard University.
During Session II of Harvard SSP 2008, the room became a legend.
It all started with "Never Have I Ever" and "Truth-or-Dare" but suddenly turned into "Dare-or-Sodemy"
Many things happened, including:
-Gay/Lesbian Sexual Activities
-Guys in Bras
-Sploshing a personal favorite of one of the tenants
-Christina bear and Sara bear getting it on
There is also a store that has opened in C21, complete with:
-Someone that just does EVERYTHING
-Owner of Keith Fucking Moon
-Someone who has retained their dignity
C21 can also be used as a verb...usually applies to anything sexual.