Madrid has no coastline and still flies a Blue Flag. The San Juan reservoir, in San Martín de Valdeiglesias, supplies two of the four natural bathing zones in the Comunidad de Madrid: El Muro and Virgen de la Nueva, the only ones rated excellent under European Union parameters. At Virgen de la Nueva there is daily supervision from noon to 8pm, with six lifeguards and two boat crews from the Red Cross.
Where can you swim at the San Juan reservoir? At two authorised areas in San Martín de Valdeiglesias: El Muro and Virgen de la Nueva, both rated excellent. The season runs 15 May to 15 September. Virgen de la Nueva holds a Blue Flag and is supervised daily from noon to 8pm by six lifeguards.
The San Juan reservoir is the only body of water in the Madrid region with two authorised bathing areas, and both carry the highest possible rating. That concentration explains why the regional list is quoted sometimes as four zones and sometimes as five points: there are four natural sites, and one of them holds two areas.
Four zones or five points
The apparent contradiction in the count has a simple explanation and is worth settling first.
The region speaks of four natural zones fit for bathing: the San Juan reservoir, the Playa del Alberche at Aldea del Fresno, Las Presillas at Rascafría and Los Villares at Estremera. But the San Juan reservoir has two areas, so counting areas gives five. Both figures describe the same thing. The full list with ratings is in where you can swim in the Madrid region.
| Natural zone | Municipality | Areas | Rating |
|---|---|---|---|
| Playa del Alberche | Aldea del Fresno | One | Insufficient in 2026 |
| Los Villares | Estremera | One | Good |
| Las Presillas | Rascafría | One | Good |
| San Juan reservoir | San Martín de Valdeiglesias | El Muro and Virgen de la Nueva | Excellent |
What supervision actually looks like
This is what sets the place apart, and it appears in neither the name nor the rating.
There is daily supervision from noon to 8pm, with six lifeguards and two boat crews running a motorboat and a jet ski for the Red Cross. Virgen de la Nueva has also renewed its Blue Flag, an award recognising visitor services, sustainability and accessibility. Nothing else in the region combines the two.
How the water is monitored
The rating comes from sustained testing rather than from a single sample.
The water is analysed every two weeks through the bathing season by the regional public health service, and this summer 52 checks have been scheduled across the four zones together. The published classification is calculated over four consecutive seasons rather than the current summer, which is why a site with clean samples can still carry a low grade.
Where not to swim
This is the warning the regional government repeats every summer, and it has an operational basis.
Only the listed points have water-quality monitoring and a supervision arrangement in season. The region warns explicitly about the danger of bathing at unauthorised spots. Mountain rivers and pools outside the list have neither, however freely you can reach them, in how Madrid rations its countryside.
What else fits a water day
Inside the city there are alternatives with their own season, useful when the trip out does not work.
The municipal summer pools run 15 May to 6 September across 25 sites at 2.25 € an adult session, in Madrid’s summer pools. For the mountains, road access runs on quotas, in Sierra de Guadarrama access. The month matters too, in the best time to visit Madrid.
Frequently asked questions about the San Juan reservoir
Can you swim in the San Juan reservoir?
Yes, at two authorised areas in the municipality of San Martín de Valdeiglesias, El Muro and Virgen de la Nueva. Both are rated excellent under European Union parameters, the best in the region, and the season runs 15 May to 15 September.
Are there lifeguards at the reservoir?
At Virgen de la Nueva there is daily supervision from noon to 8pm, with six lifeguards and two boat crews operating a motorboat and a jet ski from the Red Cross. It is the fullest arrangement of any bathing zone in the region.
How many bathing zones does the Madrid region have?
Four natural zones, though one of them, the San Juan reservoir, supplies two separate bathing areas. That is why the count appears sometimes as four zones and sometimes as five points, and both figures are correct.
How often is the water tested?
Every two weeks through the bathing season, by the regional public health service. This summer the region has scheduled 52 checks across the four natural zones taken together, on top of the annual classification.
Can you swim in any river or pool in the region?
No. The regional government warns explicitly about the danger of bathing at unauthorised spots, and only the listed points have water-quality monitoring and a supervision arrangement in place during the season.
In a region with no sea, the Blue Flag flies over a reservoir an hour or so from the centre.