The Madrid meridian is a geographical reference line that runs through Madrid, Spain. It is significant because it was historically used as a prime meridian for mapping and navigation before the adoption of the more widely recognized Greenwich meridian. The Madrid meridian is located at approximately 3 degrees west longitude. This meridian is marked by a monument in the city, known as the Monumento al Meridiano de Madrid. It serves as a reminder of Spain's contributions to cartography and navigation. The Madrid meridian is also part of the broader context of global meridians that help define time zones and geographical coordinates.