Peregrine Island is the major high-level zone for City of Heroes, with the Rikti Crash Site and Shadow Shards being rarely visited. Given that it is an island, and therefore with limited land space, this makes it often a crowded place to be. It is the home of Portal Corp, which has many missions to alternate universes, as well as an Arena. It's also the only place one can hunt Malta Operatives and Carnies out in the open.
Interesting diversions in the area include "Monster Island", filled with gigantic Devouring Earth monsters, and "Monkey Island", covered in Rikti monkeys, both to the north of the main island.