Megaprojects, characterized by their immense scale, complexity, and significant public and private investment, frequently face substantial financial and risk management challenges. Cost overruns, schedule delays, and unforeseen complexities are common, often leading to public scrutiny and economic strain. This article presents a longitudinal study of Stuttgart 21, a prominent railway and urban development project in Germany, to examine the intricacies of financial management and risk mitigation strategies in such ventures. By tracing the project's evolution from its inception to its current status, this analysis highlights key financial decisions, funding mechanisms, and the various risks encountered, including technical, political, environmental, and financial. The study identifies critical factors contributing to cost escalation and delays, assesses the effectiveness of implemented risk mitigation measures, and draws broader implications for the successful delivery of future megaprojects. The case of Stuttgart 21 offers valuable insights into the dynamic interplay between project governance, stakeholder management, and the inherent uncertainties of large-scale infrastructure development.