The area is fantastic for trail running, with routes ranging from high mountains to hot coastal trails by crystal clear seas. The possibilities are almost endless and largely unexplored. My apologies for the lack of photos, I tend to run alone so don’t take any. I’ll try to add some soon.
There are some excellent and challenging trail running races held over the summer in the region. The best resource for race information can be found at this excellent English language site dedicated to trail running in Croatia (Trail Running Croatia).
Ad Natura Sport run four of the biggest races in the region under the banner “Kvarner trails”. These are of different lengths, from 16 to 72km. Their website is here. It is only in Croatian, but all the individual race sites are available in English. The races are very cheap, well organsied and a lot of fun. Only the Risnjak event is not easily accessible by public transport. Such races can be an ideal way to add some adventure to a beach holiday and also to see parts of Croatia rarely seen by tourists.
Perhaps more usefully their routes all have routes have links to wikiloc so can be downloaded for use at any time.
The routes associated with Rijeka Trails all start at Trsat caste, within Rijeka, making access particularly easy and without any need for a car.
Kastav is a particularly picturesque and historic town overlooking Kvarner Bay. There are three marked routes through the forest for hiking, biking and running. They are roughly 4, 9 and 14km long if you don’t take the side excursions. The routes are marked with snail, rabbit and deer logos respectively but are in need of repainting. The gpx files can be found on the Rijeka Trails site and are conveniently the first three trails listed.
I particularly like these routes which can be run all year round. They are hilly routes but relatively gentle. There is a fruit shop in the main square of Kastav where the routes all start and finish which is ideal for a post-run banana. It is easy to drive to Kastav, it is well sign posted from both Rijeka and Opatija. There are regular buses from Rijeka (no. 18) and is in zone 3.
Some of the mountain bike routes on the Bike Rijeka app are also good for running. I particularly like P1 Radesevo for a shortish but hilly run.
Detailed information on routes I have run:
Cres town to Sveti Blaz – an hot run by the sea to an abandoned church
Rijeka: Skrljevo – Cavle – Use the bus to access an airy run with stunning views
Rjecina trail – follow the river from Rijeka to its source