Backyard Ultra Horizontes is a trail race in Proença-a-Nova, Castelo Branco district, Portugal, typically held in late April. Each participant begins the same 6.706 km forest-and-mountain loop on the hour, with one hour to complete it and any remaining time for rest at the Quintal, the race yard.
The format originates from Lazarus Lake’s American Backyard Ultra concept: there is no set finish distance, only another lap until a single runner remains. The Proença-a-Nova loop includes approximately 110 m of elevation gain per circuit. The event attracts endurance athletes, their support crews, and companions into a communal atmosphere. Proença-a-Nova previously hosted Portugal’s inaugural Backyard Ultra and a national team qualifier for the global Backyard championship.