The town of Mayorga in Valladolid is home to an array of medieval architecture, including the churches of Santa María de Arbas and San Salvador. Mayorga is also known for its traditional festivals and local cuisine, which give a taste of authentic Spanish life. On an exterior brick wall of an old home, you can find a plaque and a small slit, marking the oldest working letterbox in Spain. The stone mailbox was installed in 1793, and is accompanied by an inscription indicating its 18th-century origins. Its installation was part of an effort…