The ancient city is spread out over about 4 km north to south, with most major buildings strung along a single road through the archaeological zone. A bicycle is the best way to see it — flat, shaded, and cheap to hire near the ticket office. Plan on three to four hours to cycle the full circuit at a leisurely pace.
For the energetic, walking is feasible if you stay near the Quadrangle and the Royal Palace and miss the northern stupas. The most convenient option for travellers in a hurry is to take a tuk-tuk by the half-day, which lets the driver wait at each site while you wander. Sun protection is essential: there is little shade between the major monuments.