While I have been to the Duomo in Milan, including many of its nooks and crannies (thanks to the late and great Msgr. Angelo Amodeo who was our estimable tour guide) there were a few mysteries that remained for me about it architecturally, mainly as regards the original sanctuary and high altar prior to its post-conciliar renovations.
Most of those have recently been lifted for me as I came across a cache of historical photos on the Italian forum Cattolici Romani which show how the sanctuary originally appeared, how the original high altar was dismantled and how part of it was further moved forward into the sanctuary toward the nave -- thereby explaining some of the architectural disconnects.
Here, first, is a view of the historical altar itself.
As we move back from the altar, we get a better sense yet:
Here is an old illustration.
Now, having seen these, here is a view of the sanctuary in transition -- likely in the latter half of the 1960's. One can still see the original high altar in tact here with a new freestanding altar pushed forward as was typical within this period.
And here is the altar and sanctuary today. One can see what remains of the original high altar (namely the tabernacle and its canopy) which has been pushed forward within the sanctuary and which has been reversed from its original position. Behind is now a sort of chapel.