Istria is small enough to loop in a day but worth two, and a car is the only way to do the hill towns justice. From Pula you can reach any point in the peninsula in about 90 minutes, so the question is not distance but which stops you actually want. Here is a loop that works.
The shape of the loop
Leave Pula north along the coast to Rovinj for a coffee, then cut inland to the hill towns: Motovun on its ridge, Grožnjan the artists’ village, and the truffle country around Buzet. Drop back to the coast at Poreč or Novigrad, then run south down the coast road home. That is a full day if you stop, two if you sleep inland.
The hill towns
Motovun and Grožnjan are the two to do. Both sit above the Mirna valley, both are pedestrian-only in the core, and both have the same problem: parking is at the bottom of the hill, and you walk or shuttle up. Go early, because the lanes clog by midday in summer. The Istria travel guide covers the region in full, and the day trips from Pula guide has the car-free versions if you would rather not drive.
Driving notes
Croatian rural roads are narrow and the locals drive them fast. A hire car for the loop costs less than the sum of the tours, but only if you are comfortable on single-track bends. Fuel is cheaper than in most of western Europe, and the toll roads are limited, so budget for time, not money. Parking in the hill towns is the real cost, not the fuel.
Where to sleep
Base in Pula and do it as a loop, or take a night in a hill-town guesthouse to eat somewhere quiet. Our where to stay in Pula guide covers the city base, and the getting around Pula page has the car-hire maths. The honest bit: the loop is better as two days than one, and the inland stops close early, so start before nine.
