The K3 Ultra Gold Border Race traverses the Rhodope Mountains border region, high above Zlatograd. This trail event, noted as Bulgaria's first ultramarathon of its kind, uses old "hajduk" paths, reflecting a rugged mountain ultramarathon character. Participants run the course during one of autumn's most colorful and scenic times, ending in Bulgaria's southernmost town.
The course is crafted for ultra runners who genuinely appreciate the outdoors, beyond simply accumulating distance. It presents striking vistas and challenging sections, passing by medieval fortresses and chapels including Kechi Kaya, St. Athanasius, St. Nedelya, St. Catherine, and Sts. Constantine and Helena. Runners are offered 360-degree views of the Rhodopes, with distinct points allowing simultaneous observation of both Bulgaria and Greece.