Even on a tight schedule, Gendarmenmarkt earns the hours.
Allow 20–40 min.
The symmetry of the French and German cathedrals flanking Schinkel's concert hall is genuinely elegant, free to enjoy, and lovely at golden hour. The catch: it's a 'look, don't do' square, has seen long renovation works on the paving, and there's little beyond the view unless a concert or Christmas market is on.