One entry, an hour up the strait from everything the guidebooks send you to, and the journey is not the price of the visit — it is the visit.
One entry makes a short day on paper. The water lengthens it, agreeably.
Go by boat. I say it on the country page and I will say it here, because everyone is told the road is quicker and everyone who takes it arrives in a worse mood. The ferry up the strait is the correct approach, and the houses along the way set you up for the one you have come to see.
October suited it exactly — clear light off the water, cool enough to keep walking, and a crowd that was exemplary in the sense of barely existing. Summer would be a different and busier proposition.
Do not treat this as a morning to be got through before the old city. It sits at the far end of a long day in the opposite direction; give it the day, come back on the water at dusk, and let the famous things wait for tomorrow.