Hi, I'm driving from Zagreb to Motovun one day, and am wondering about whether to go straight across northern Croatia or swing a northern arc through southern Slovenia - map says it's less than 30 min diff total on the main roads. We're happy to do whichever will give us the best scenery and maybe an interesting stop along the way, but don't want to spend the whole day to make the trip, to have more time in Motovun as well. We'll get to Slovenia another time, so I wouldn't go just to cross it off the list. Just wondering if anyone has made the trip, or knows enough of the areas to recommend either way. Thank you!
I have no personal experience with either route, but you can go to ViaMichelin.com, enter your origin and destination and it will propose one or more routes for you. Michelin's maps highlight scenic roads in green. You may need to zoom in to see it clearly.
I've been on parts of the two main routes between Zagreb and Motovun and they're primarily expressways. I'd give the edge to the Slovenia route as it goes through the Karst region. There are some castles and cave complexes not far off the Karst portion of the route that would make for an interesting stop. I visited the Skocjan Caves, but there are also caves and a castle near Postojna. The Lipizzaner farm, which I didn't visit, is very near the Skocjan Caves. Rick's Croatia & Slovenia guidebook has good coverage of these sights. My recollection is that I had to buy a permit to drive on Slovenian expressways, but it's been a few years so I don't recall the specifics or know whether that's still the case.
If you have half a day to do the trip, you can stop along the way in some very scenic places in Slovenia. Frank has given you some great suggestions for the latter half of the drive, between Ljubljana and Motovun. Before Ljubljana, you could also consider a stop at Otocec Castle or in Novo Mesto. I would not stop in Ljubljana as the city deserves at least a full day, especially if you'll be returning in the future. In the Slovenian portion of Istria, quite close to your route to Motovun, there's also the Romanesque church in Hrastovlje and its Dance Macabre frescoes.
In terms of cost, it's about the same either way - the tolls through Croatia are about 100 HRK (€15) altogether, while the vignette (toll sticker) for Slovenia costs €15. Make sure you buy it at a rest area or gas station in Croatia or at the rest area right after the border at the latest - you are required to have it applied to the windshield before driving on the highways or you risk receiving a fine.