GM4O 40.6km: Slovenia’s Most D+-Dense Mountain Marathon, WMRA World Championship Heritage, and 25 Editions in Baška Grapa

The GM4O is one of the most gradient-intense 40km courses in the DiscoverTrailRaces catalogue. At 76.35 m/km D+ (3,100m across 40.6km), it ranks in the top 4% of ~390 courses by climbing density — only 14 courses have more D+ per kilometer. The average uphill gradient ranks in the top 7% globally (27 of ~390). The average downhill gradient ranks among the top 3% most demanding (378 of ~390 on a gentleness-ranked scale where rank 1 = gentlest). Only 3.52% of the course is flat. This is a course that demands extreme technical mountain movement — both up and down severe gradients — across 40km with almost no gradient recovery terrain between features.

In 2025, Tine Žimond (KGT Papež) won the men’s race in 4:13:11. Barbara Jolić (Šmarnogorska naveza) won the women’s race in 5:09:58. The 2025 race served as the Slovenian National Short Trail Championship, adding a championship layer to the event. Complete finisher count for 2025 is not confirmed in our records — full timing results are available at the Timing Ljubljana website.

The GM4O hosted the 13th WMRA World Long Distance Mountain Running Championships in 2016, and the 8th WMRA World Long Distance Mountain Running Challenge in 2011. WMRA world championships are held on courses that meet strict international technical standards for mountain running terrain — sustained natural climbing and descending on mountain trails at high gradient. Hosting twice places this specific course in a very small global cohort of elite mountain running venues. For runners using the DTR database to find world-class mountain terrain, this is the clearest external validation the GM4O course can receive.

The Gorski Maraton Štirih Občin (Mountain Marathon of Four Municipalities) has results on record from at least 2002 and celebrates its 25th anniversary in the 2026 edition — making it one of the oldest mountain running events in Slovenia. The race is organised by Turistično društvo Podbrdo, the local Tourism Society of Podbrdo, a volunteer community organisation that has shaped the event across its full history. The Baška grapa valley is identified by race organisers as the site of the first mountain run in Slovenia, held in 1970. The Podbrdo Trail Running Festival has since grown to three distances (40.6km, 70.1km, 103.8km) but the GM4O is the founding event.

Ljubljana Airport (LJU) is approximately 68 minutes from Podbrdo — well inside the DTR "not far" threshold. Trieste (TRS) and Venice Marco Polo (VCE) are both viable alternatives for runners arriving from Italy or western Europe. Public transport by train or bus to Most na Soči is possible, then local taxi or ride-share to Podbrdo village. A car is strongly recommended: the Baška grapa valley has limited local transport frequency. Accommodation in Podbrdo village itself is limited — recommended bases are Tolmin (approximately 20 minutes away) and Bohinj (approximately 40 minutes), both with good infrastructure for race weekends. Book early: the June GM4O weekend coincides with peak summer demand across the Soča valley region.