Hidden 48 meters below the busy streets of Madrid lies one of the most extraordinary security installations in Europe: the gold vault of the Bank of Spain. For more than 77 years, no robbery attempt has ever been made. With massive armored doors, a unique hydraulic flooding system, and layers of reinforced construction, this chamber has become a global benchmark for high-security engineering.

An Underground Fortress

Excavated in solid rock and surrounded by reinforced concrete, the vault is accessible only through a sequence of stairways, security locks, and massive armored doors. Designed during the 1929–1936 expansion under architect José Yarnoz, the project used depth and mass as primary protective barriers against explosives and drilling attempts.

The Hydraulic Flooding System

One of the most unique features of the vault is its flood defense mechanism. Two underground water streams—Las Pascualas and Oropesa—can be diverted to flood the access corridor in the event of an intrusion. In a submerged environment, electrical and thermal tools become useless, buying precious time for security teams and making entry nearly impossible.

Armored Doors and Security Protocols

  • 15–16 ton armored doors built from rust-resistant steel, maintained twice a year to ensure airtight sealing.
  • Multiple-person access: each door requires two keys and two separate codes held by different officials.
  • Redundancy: no door opens until the previous one is securely locked.

Where Spain’s Gold Sleeps

Inside the chamber rest around 5,400 standard gold bars of 12.5 kg each, stored on shelves designed by engineer Eiffel. In total, Spain holds about 281 tons of gold—equivalent to 9.1 million troy ounces—worth more than €12 billion. A third of this gold lies in Madrid, while the rest is distributed between Fort Knox (USA) and London.

Surveillance and National Heritage

Of the 2,500 m² facility, 1,500 m² are usable due to massive dividing walls. A unique mirror corridor around the vault allowed guards to detect any silhouette without patrolling the entire perimeter. The Bank of Spain also keeps its vast numismatic collection here, with over 500,000 coins and nearly two million gold-valued pieces, alongside secure areas for government institutions.

The Gold Sale Controversy

Between 2004 and 2007, Spain sold nearly half of its gold reserves, reducing them from 523 tons to the current 281 tons. The move was justified as diversification into more profitable assets but sparked debate among experts, who emphasized that gold remains a timeless safeguard against devaluation. Since 2007, the reserves have remained stable under European Central Bank agreements that limit gold sales to protect the market.

A Vault Built to Survive

The Bank of Spain’s gold chamber is not only a secure facility—it is also a resilient bunker. It withstood bombings during the Spanish Civil War and served as a shelter for employees and their families. With its combination of depth, massive armored doors, flood defenses, and redundant protocols, it stands as one of the safest vaults ever built.

Inspiration for Arcas Gruber

At Arcas Gruber, we draw inspiration from legendary facilities like the Bank of Spain’s vault to design and manufacture our own high-security solutions. Our safes, Euro-Grade safes, and certified wall safes are built with the same principles: multilayer resistance, redundant locking systems, and advanced detection. Manufactured in Europe and exported worldwide, they protect banks, industries, governments, and private clients.

The underground vault of the Bank of Spain is more than a storage site—it is a monument to security engineering. With its depth, hydraulic defenses, and colossal doors, it remains an international benchmark. At Arcas Gruber, we apply these principles to deliver the highest levels of protection in our safes and armored chambers, designed for today’s global security needs.