Each district has different side missions players can complete in Marvel's Spider-Man. These appear as blue icons on the map and are optional missions provided to the player as they enter or unlock specific regions. Some side missions are unlocked through story progression while others take a bit more work. They are typically assigned to Spider-Man by a particular citizen of New York City, and award experience points upon completion.
Unlocked during the story after sleeping on Aunt May's couch in the mission Couch Surfing. Talk to Howard afterwards and he reveals that his pigeons are missing. After unlocking the mission, the map will have bird icons indicating the locations of the missing pigeons. Locate them and bring them back. Fast travel makes this mission much easier.
Unlocked after completing the mission Spider-Hack. Spider-Man must track down a college friend with only a photograph to go on. Climb to the roof of a tall building and look for a fire in the distance.
This can be unlocked after completing Over His Head. Locate the missing person using only a photograph. The missing person is the leader of the Debate Club and is located in the east side of the Financial District.