The main plan of Avengers: Endgame for solving what Thanos did in Avengers: Infinity War involves the
As part of the plan Tony misplaces
and so he and Cap have to go looking for it elsewhere. They decide to go back to
a SHIELD base in 1970 where both the Tesseract is stored and Hank Pym is based working on the Pym Particle. Whilst there Tony also bumps into his father, Howard Stark, working on the base.
Tony and Cap have a conversation in hushed tones about choosing it and it seems to be that they both know about it. Is there anything special about this place and time and how did they both know about it?