The 100K Madrid-Segovia is an annual point-to-point ultratrail connecting Spain's capital with Segovia. The full Xtreme route spans approximately 101-102 km with over 2,000 m of elevation gain. It begins in Madrid and concludes under Segovia's Roman Aqueduct, transitioning from city streets to Guadarrama mountain terrain before descending into a historically significant area. Shorter race options are also available: 65 km from Madrid to Cercedilla, the 42 km Maratón del Castillo, and the 21 km Medio Maratón de la Sierra.
The full route utilizes livestock tracks from the Madrid section of the Camino de Santiago. It passes through Monte de El Pardo, Colmenar Viejo, the Castle of Manzanares el Real, Puerto de la Fuenfría, ten municipalities, and Guadarrama National Park. The Xtreme race has an 18-hour time limit, eight aid stations, and around 400 participants, positioning it as a challenging mountain event rather than a city ultra. The Madrid-Segovia name is also used for a non-competitive cycling event, featuring long point-to-point routes from Madrid towards Segovia and a shorter option finishing in Cercedilla.