Vivos Europa One is the company's 76-acre (31ha) flagship compound in Germany. It was carved from the bedrock beneath a 400-foot (122m) mountain by the Soviets during the Cold War.
The now-renovated space includes gymnasiums, theatres, bars and pools with over 228,000 square feet (21,181sqm) of living areas.
The complex is no longer accepting applications from potential residents, however, back when spaces were available, the cost for a private apartment started at €2 million (£1.7m/$2.2m).