K3 Ultra – Gold Border Race is the first ultramarathon in Bulgaria that takes place in the border region of the Rhodope Mountains. The event takes place at the end of September, one of the most colorful and picturesque periods of autumn. The marathon finishes in Zlatograd, the most southern town in the country. Participants can choose from several different distances. Along the route, they will enjoy stunning views and adrenaline-pumping sections, passing through medieval fortresses and chapels such as Kechi Kaya, "St. Athanasius," "St. Nedelya," "St. Catherine," and "Sts. Constantine and Helena." The routes offer 360-degree panoramas of the Rhodopes and the opportunity to view both Bulgaria and Greece simultaneously.