Bola del Mundo, also known as Alto de las Guarramillas is a mountain of the Guadarrama mountain range located in the Community of Madrid in Spain, near the border with the province of Segovia. Its height is 2,257 meters (some sources give it 2.265 meters). It is one of the hardest climbs ever seen in pro cycling. Despite its modest average gradient of 6.2%, the climb gets really hard in the final kilometers where average gradient is always above 10% and at some points it gets as steep as 19%.
These three large antennas are covered with a warmed-up radom in the form of a missile that protects them from frost, are visible from a distance of several kilometers and are the most peculiarities of this mountain, which is very easy accessing from Puerto de Navacerrada. At present, the number of antennas has dropped a lot shortly after being shot down by the strong winds affecting the area on several occasions, and it is not excluded that they will completely disappear in the future when they lose their function and will be replaced by satellite telecommunications.