From Paragon Wiki Archive
Supergroup's base, the bases of any Supergroups they are coalitioned with, and the base of their team's leader, provided that the individual has permission to enter the base. A Base Portal is located in each city zone in both City of Heroes and City of Villains, except hazard, trial, and Player vs. Player zones.
Base Portals are denoted by a "P" inside a green circle on game maps, and generally look like purple cylinders with ethereal lighting effects around them.
Using a Base Portal takes the person to the Entrance Room of the base.
The Base Portal is also a day job location. If you log off in any Supergroup Base, you will emerge from the Base Portal upon log-in, earning credit toward the Monitor Duty day job.