The historic core of Milan, the ground the city has occupied since Roman Mediolanum, organised around the vast marble bulk of the Duomo. This is the Milan that visitors picture: the cathedral and its square, the glass-vaulted shopping arcade beside it, the opera house, and the tight grid of streets that held the medieval and Renaissance city before the ring boulevards were built over the old walls.
Piazza del Duomo is the pivot. From it the Galleria Vittorio Emanuele II — the 19th-century iron-and-glass arcade — leads through to Piazza della Scala and the Teatro alla Scala. South and west, narrow streets thread past the optical-illusion apse of Santa Maria presso San Satiro, the bone-lined chapel of San Bernardino alle Ossa, and the Museo del Novecento with its collection of Italian 20th-century art overlooking the cathedral square. It is dense, walkable, and almost entirely pedestrian at its centre.
Everything here is within a few minutes' walk, which makes it the obvious place to start. It is also the most crowded part of the city, and the cafes on the main square charge for the view. Step one street back — toward San Satiro or the quiet lanes around the Verziere — and the prices drop while the architecture stays just as good.