The appearance of an ancient stone inscribed with «Acotado M. V» in the Fuente del Sapo stream, in Alcorcón, has captured the attention of José Luis, a journalist skeptical of local stories. Initially, the find seemed to be a simple curiosity, but the mention of the initials, corresponding to the Marquis of Valderas, piqued his interest.

The landmark, an irregular and weathered stone, barely protruded from the ground in a cordoned-off area. A local resident told José Luis that the stone marked the boundaries of the Marquis's estate, but added that “it shouldn't be here” because “that wasn't the limit.” This statement led the journalist to review ancient documents, maps, and records of the marquisate, discovering that the stone's location did not match the historical boundaries of the property, which extended much further west.

On a second visit, José Luis found the stone “cleaner,” as if it had been unearthed overnight. Upon closer inspection, he noticed a straight line and other marks suggesting the stone was part of something larger. A dream about the castles of San José de Valderas, built between 1915 and 1917 as the Marquis's residence, gave him a new perspective. When he drew a line from the landmark to the castles on a map, the coincidence was not exact, but neither did it seem random.

José Luis's investigation revealed that the landmark did not mark an outer boundary, but an irregular, enclosed perimeter, possibly an inner limit of something still unknown. During a nighttime visit, the stone felt cold like metal, and he heard a sound. The lines on the stone became clearer, forming a precise geometric pattern. The next day, the City Council had removed the landmark. The same neighbor from the first day, carrying a cane with the initials «M. V», told José Luis that the stone “shouldn't have been here” and that it was now “where it doesn't bother anyone,” leaving the journalist with the feeling that an invisible line continues to mark boundaries yet to be discovered.