This final point lies on the south-western edge of Madrid, near Arroyomolinos and Navalcarnero, a long way from the Alto Tajo itself. The natural park that gives the ride its name is some hundred and fifty kilometres to the east, in the high limestone country on the borders of Guadalajara and Cuenca provinces, where the Tajo and its tributaries have cut deep, tree-lined gorges through a plateau of pale rock. Here, you are back in the commuter belt, among new housing estates and fields of cereal and olive.
Navalcarnero deserves a stop if you have any energy left, because its Plaza de Segovia is a proper arcaded square, built in brick and timber, with galleries on all sides and the feel of a small Castilian market town. It is also known historically as the place where Charles II married Marie Louise of Orléans in 1679, a royal wedding in the middle of nowhere, and the local wine, a rustic Madrid red, has been drunk here for centuries. Arroyomolinos is mostly modern, but it does have some old cork and holm oak in the surrounding land.
The Alto Tajo you rode in the morning is something else entirely. The river runs a rich turquoise between cliffs, with griffon vultures wheeling overhead, juniper and pine on the slopes, and high plateau roads that feel closer to Aragon than to Madrid. The gorge roads there are often narrow and empty, with the occasional village such as Poveda de la Sierra or Peralejos de las Truchas hidden in the folds of the hills. Fuel stations in that area are scarce, so you will have been glad of a full tank at the start, whereas here, with Navalcarnero's twenty thousand people and Arroyomolinos beside it, you are never far from a pump, a bar or a supermarket.
Traffic is the main hazard at this end of the day. The A-5 and M-50 get sticky in the evening and in summer the tarmac holds heat long after sunset. Take it calmly, let the tired muscles unwind, and think about those turquoise gorges while the brake lights glow ahead.