Koper's old town is compact enough to explore thoroughly in a morning. The anchor is Titov Trg — the main square, surrounded by Venetian Gothic palaces — from which the narrow medieval streets of the old city radiate in every direction. The Praetorian Palace, the Cathedral and Bell Tower, and the Koper Regional Museum are all within a few minutes' walk.
The city has real architectural depth. Koper was Venetian for centuries, and the old town retains the character of an Adriatic trading city: narrow passages, carved stone doorways, the remains of a loggia, palaces whose owners' names are still on the buildings. Walk slowly and look at the details.
Beyond the old town, the Muda Gate marks the historic entrance to the city. The Da Ponte Fountain, just beyond it, supplied fresh water to the island city for centuries. For day trips, Piran is 45 minutes south and Trieste is 20 minutes north — Koper sits at one of the best crossroads in the northern Adriatic.