TITLE: Using algebraic geometry to understand class field theory
QUESTION [33 upvotes]: In Algebraic Number Theory, S. Lang says "[a geometrical approach] allows one to have a much clearer insight into the whole class field theory, since the existence theorem and
the reciprocity law become obvious once the machinery of algebraic
geometry is available."
Inspired by this, I wonder if there is some (preferably modern) reference for class field theory using algebraic geometry.

REPLY [3 votes]: I would like to point out a letter from A Grothendieck to L Breen
[pdf]
In which he explains some details about it. See for example page 45