with ww2 small Little Boy or Fat Man 10~20kilo tons of TnT, no problem they will rebuild the city,
call international Architects like Le Corbusier, Walter Gropius, Mies van der Rohe or Oskar Niemeyer to make master plan for new Berlin.
with huge monument for deaths for first use of Atomic bomb.
With Cold war nuclear weapon of 1960s & 1970s, its hell different problem
there are Large Caliber max 9000 kilo tons of TnT and design to be very dirty in radioactive waste.
in this case Berlin would for over 30~60 years a no-man land with deathly radiation.
With 1980s nukes again the "game" change down to small caliber max 1000 kilo tons of TnT, but used massive.
it would change Berlin into "ground zero landscape" were several nukes hit the city.
here they could rebuild the city, but the rest of world would look the same.
see best TL of 2010: Protect and Survive
Also is there use of neutron bomb, like name say it produce massive burst of neutrons what kill all live in it's range, but with little damage.
A depopulate but intact Berlin...