The city centre is walkable. From Lions Square to the harbour is about 15 minutes on foot; the Archaeological Museum is 5 minutes from the square. The Venetian walls encircle an area compact enough to cover on foot in a morning.
For Knossos, take city bus 2 from Lions Square — it runs every 20 minutes and the journey takes about 20 minutes. A taxi is around €10–12 each way.
Car hire is useful for exploring eastern and central Crete from Iraklion as a base. The national road runs east toward Agios Nikolaos and west toward Rethymno and Hania. Parking in the city centre is difficult; most visitors park near the old harbour.