As the tunneling industry continues to adopt Tunnel 4.0, digital twins of the tunnel construction site are becoming standard requirements for tunneling projects. However, the benefits of these remain unproven to many practitioners. This article discusses the various implementations of digitalization and describes efforts to combine all data types to analyze the relationships between influences, predictions and performance in a single digital platform. This includes data pertaining to investigations, design, construction, monitoring and post-construction asset performance and management. Based on 16 years of global tunneling projects this article aims to quantify the tangible and intangible benefits of such systems. Using a number of real examples, this article describes where opportunities were taken and where they went unrealized. Challenges and considerations for both procuring and developing these digital twins are also discussed.