The Taça Intermunicipal 3H Resistência BTT is a six-round mountain bike endurance series held in the greater Lisbon area, with events in Alenquer, Loures, Mafra, Oeiras, Amadora, and Lisboa. Each round consists of three hours on a local circuit, with the winner determined by the number of laps completed rather than a point-to-point race. The series begins in late May and concludes in the second half of the year.
The series takes place at various municipal locations, such as Jamor in Oeiras, Monsanto in Lisboa, Amadora, and Mafra, offering participants a distinct local course at each stage. It accommodates a broad range of participants, including youth riders, masters, general mountain bikers, and e-bike racers, with a dedicated youth race held alongside the main event. Following the six stages, the season concludes with a final awards ceremony.