Hello. My wife and I spend two days in Kobarid then drive to Piran for one day. Please suggest sightseeing and activities in the respective towns and on the route.
Kobarid: The Kobarid Museum, Kolovrat WWI open air museum are my two big sights. The mausoleum takes only a few minutes to see. Slap
Kozjak is a great, very manageable hike.
Piran doesn’t have sights so much, but it’s oozing with atmosphere and is a treat to explore. Fritolin Pri Catini is a terrific place for lunch, dinner can be super busy. Srebrna Villica does great, elevated Italian.
Are you day tripping to Piran, or staying the night? If it’s not a day trip I would see Skocjan caves on the way. It’s about halfway with a timed entry ticket.
Great combo! For the Kobarid–Piran leg, the drive is roughly 2–2.5 hours depending on route. If you're not stopping to day-trip Škocjan, going via Nova Gorica takes you right past the Vipava Valley — a nice detour if you have an extra hour, with small family wineries doing tastings of local Pinela and Zelen (much quieter than the coast). I saw a good rundown of the wine stops there on this site if it helps with planning: https://tipsinslovenia.com/slovenian-food-wine/slovenian-wine/vipava-valley/.
If you'd rather fit in Škocjan/Predjama en route, the road via Sežana is faster (timed tickets needed for Škocjan, as awrzesinski mentioned). As for Piran — one day is enough to wander, but if you can swing an overnight, sunset from the town walls or Punta point is worth it, and the day-tripper crowds thin out noticeably by early evening.