More than an hour away from Madrid (about 80 km), in the middle of the El Burguilo reservoir (Ávila), there is an island complete with a castle. Called Sentinella, it occupies 10,847 square meters and, according to Avila Red, is for sale for €3.25 million on Idealista, where it has been advertised for years. In fact, we just checked Fotocasa’s price history and it’s even cheaper than it was a few years ago. If you have a few extra euros lying around and want to feel like an uncourted king, you’ll have four floors with an elevator and dozens of amenities in return. Of course, the island was not always the same and even the age of the fort is disputed.
What’s inside. The palace is built around 1,000 meters, with crenellated towers, terraces and floor-to-ceiling windows. At its heart are seven outdoor suites, each with a signature fireplace and some with a Jacuzzi. A large party pavilion with a professional bar counter converts to four more bedrooms. Thus 11 bedrooms and 11 bathrooms appear on the technical sheet. Outside there are ditches, trees and its own pier.
self contained The island operates on its own: solar panels, two backup generator sets and its own water purification and filtration system. The ad also mentions a heliport, but as a possibility, not something that exists today. You can go deeper into its sustainability model in this video. And what is there is a pear.
boat or car. The usual access, in fact, is by boat from the private pier, about 300 meters from the shore. El Burguilo occupies 910 hectares behind a 91-meter dam, stores about 198 cubic hectometers and has a very marked dry season: its average level usually drops below half. Then, as announced, the island meets the mainland and you can reach the reef itself by vehicle.
How often? The advertisement talks about the months in which the level drops. The owner, Yolanda Merino, said in 2022 that the isthmus only appears every seven years. So depending on who you ask, we’re looking at a seasonal or seven-year island.
Before there were mountains. Before becoming an island, it was a peak in the Alberche valley with a watchtower before the reservoir. What separated the water, but when? Official data date the reservoir’s opening in 1913. Other sources say that work began that year and that the island was born when the valley flooded in 1926. Some chronologies point to 1927.
The age of the fort also does not match. Advertisement on an old watchtower dated 1923. The family that owns it says otherwise: Fernando Marino bought the island in 1979 and raised a wall, built a fort, planted fruit trees and vines and installed a pontoon for his boat. He sold his company and started the project at the age of 60. “The island was my father’s dream,” his daughter explains.
House wine. Merinos spent long hours there, barbecuing and making Grenache wine from the island’s grapes. A fort is expensive to maintain, so they rent it along with a rowing boat to cross the 300 meters. The rental sheets speak of the aforementioned 300 square meters, four double rooms and 10 beds (38 including glamping), compared to the 1,000 meters of sales.
Hotel with papers. There is a way to make money fast and it takes advantage of your growth as a business. The island appears in the tourism registry of Castilla y León as a three-star rural hotel, with six double rooms, six extra beds and twelve beds. Its services include a restaurant, conference rooms, elevators and even a nightclub. It also marks it as a historic building. So the bedrooms are four on rent, six on registration, seven on sale and eleven with pavilion.
wall of truth The island is completely walled, with a granite wall between three and four meters high and only three doors, leading to the beach and pier. Like most castles it usually has a “360 degree” view. In 2024 they compared it to Trakai Castle (Lithuania), which was built between the 14th and 15th centuries on an island in Lake Galway and presented as the only island castle in Eastern Europe.
Price, another tide. Although they announced in 2024 for 3.5 million and less than three, today it costs 3.25 million (in line with some Greek islands that Greece put up for sale in the middle of the debt crisis). Whoever buys it will inherit a philosophical dilemma: Is it still an island if it’s reachable by car?
What is clear is that it costs far less than some of Ibiza’s largest Catalan farmhouses or mansions, such as Marbella’s Villa Bellagio, which sold for 70 million. No need to go that far though: there are dozens of constructions in Madrid that exceed 10 million euros. It allows you to buy three islands.
Cover image idealist
In Xataka | For 60 years, a peasant with no idea about architecture built a cathedral from scratch in Madrid. Bureaucracy has stopped it
