Prague's historic core, straddling the Vltava river, is small enough to cross end to end in under an hour, with Old Town, the Jewish Quarter and Lesser Town all connected by short, walkable stretches. The famous Charles Bridge is the natural link between the two riverbanks and is always busy with pedestrians rather than traffic.
Castle Hill is the one serious climb in the city, with a steady uphill walk or a set of stairs leading to Prague Castle and some of the best panoramic views over the red rooftops below. Most of the rest of the centre is comfortably flat or gently sloped.
Cobblestones are everywhere in the old quarters, and they can be uneven and slick in wet weather, so footwear matters more here than the distances themselves. Crowds around Astronomical Clock and Charles Bridge peak at set times, so early starts help.