The document discusses the Medieval Wall built between the 11th and 12th centuries in Madrid, Spain. It had a length of approximately 2,200 meters and a total of 130-140 towers. The wall had four access doors - Guadalajara, Valnadu, Moros, and Cerrada. Each tower stood 10-15 meters high. It was the principal defensive structure for the city located at Calle Mayor #49 until burning down in a fire in 1582.