Digital Realty MRS3 (Interxion Marseille 3)

The story

In 1943 during the Second World War, the German military built the colossal 'Martha' submarine pen in Marseille's commercial harbor, encasing U-boat slips in 5.5-meter-thick bombproof reinforced concrete. Left abandoned for decades, Interxion (now Digital Realty) transformed the bunker into MRS3 in 2020. The 7,100 m² facility uses cold underground runoff from the 19th-century Gardanne mining tunnel for river cooling, achieving high energy efficiency while anchoring Marseille's boom as the primary Mediterranean subsea landing port connecting Europe to Asia and Africa.

Notable

• Constructed inside the massive 'Martha' U-boat bunker built by the German Kriegsmarine in 1943 during World War II.
• Reinforced concrete roof measuring 5.5 meters thick designed to withstand allied heavy aerial bombing.
• Cooled by a 100% natural water system drawing 15°C water from the historic Gardanne mine water drainage tunnel.
• Serves as the European termination gateway for submarine cables linking Europe, Africa, the Middle East, and Asia.

Expansions

• 1943: constructed as Nazi Kriegsmarine submarine bunker Martha
• 2020: Interxion opens 7,100 m² data center inside converted submarine pen
• 2022: MRS4 announced on adjacent port land expanding Mediterranean hub