No special access issues
To reach the Pantano de San Juan from Madrid by car, start by taking the A-5 (Autovía del Suroeste) heading southwest. After about 30 kilometers, exit onto the M-501, also known as the "Carretera de los Pantanos." Continue on the M-501 for around 40 kilometers, passing through towns such as Navas del Rey and Chapinería.
Once you arrive in San Martín de Valdeiglesias, follow the signs for the M-957 and drive approximately 6 kilometers until you reach the reservoir. The full journey is about 70 kilometers and usually takes around 1 hour and 15 minutes, depending on traffic.
When you arrive, you'll find parking areas near popular beaches like Playa Virgen de la Nueva and Playa El Muro, which offer restaurants, picnic areas, and water sports facilities. From the parking next to the church the fist walls are about at a 5 minutes walk.