Much more than just having Avengers Tower in the New York skyline, the movie establishes that the titular hero’s famed amulet — the Eye of Agamotto — is actually one of the Infinity Stones (specifically, the Time Stone).
For the most part, Scott Derrickson’s Doctor Strange exists in its own corner of the Marvel Cinematic Universe… but it does have a major contribution to the larger franchise.
Given Marvel Studios’ history, you might think that this was some big idea that has been in the works since 2006… but the reality is that the Stone was included because the Eye of Agamotto from the comics was just too powerful.