This is Auditorium A of the Niels Bohr Institute in Copenhagen in 1930.
Among the seated yappers are Bohr, Heisenberg, Pauli, Gamow, Landau, Kramers, Waller, Peierls, Bloch, Ehrenfest, Teller...perhaps the greatest collection of physicists ever gathered?
Here is the same auditorium today. It's unchanged, which is, of course, fittingly romantic, but I must say the benches aren't big enough to lodge laptops, and the coffee room is a Spinal Tap-esque adventure to get to.
We just finished a neutron data workshop in Auditorium A. This was, needless to say, a useful topic, but somehow we didn't quite reach the pinnacle of enlightenment of our predecessors, as they established the Copenhagen Interpretation of Quantum Physics.....