Broadcast from the top of the TransAmerica Pyramid

Hear me, my X-Men. This message is reaching every known mutant in the world. Good, bad, friend, foe… whoever you are. We want every mutant left to know this: the X-Men are very much alive. And San Francisco is now a mutant sanctuary. Any of you – and your families or loved ones – are invited to join us here and know safety and protection our kind has never known.

Scott Summers

And it makes perfect sense. There is no city in the world that would fit the role better, I think.