A museum project approved in July 2000 with a budget of 61 million euros and an opening date set for 2004, the Confluences Museum in Lyon finally opened on December 20, 2014, with a total cost of 330 million euros. Originally intended to house the collections of the Museum of Natural History of Lyon and the Guimet Museum, the project was initiated in the late 1990s and promoted by Michel Mercier, a local politician. At the time, the estimated cost was 400 million French francs, which equated to the 61 million euro figure. The 2004 opening date was considered achievable, but the museum would ultimately open ten years later, with an additional 269 million euros spent. The main challenge arose from a conflict between the architect and the construction company. In 2005, the company Bec, part of the Fayat group, was selected to build the museum. However, construction did not begin until 2006 and lasted only a few months before being halted. In 2008, Bec abandoned the project due to disagreements with the architect and an underestimation of the structure's weight. The museum’s nickname, the "Crystal Cloud," referred to its unique, glass-like design, which required deeper foundations than originally planned—31 meters instead of 19. This technical complexity, combined with poor communication between the architect and the contractor, led to repeated construction delays and increased costs. In 2010, the project was handed over to Vinci, a major construction company, which worked with specialized firms to rebuild the structure. The new contractor inherited a complex and delayed project, and the Rhône general council attempted to shift part of the financial burden onto Vinci by claiming a 41.3 million euro penalty for delays. Vinci disputed this, arguing that the original design plans were not detailed enough. Despite these issues, the museum finally opened in 2014 after years of setbacks and rising costs. The project’s budget had increased multiple times over the years, from 61 million euros in 2000 to 330 million euros by the time of its opening. Compared to other major French cultural institutions like the Quai Branly Museum or the MuCem in Marseille, the Confluences Museum was significantly more expensive. The museum, now owned by the Lyon metropolitan area since 2015, has become one of the largest in France outside of Paris, housing over three million objects and attracting more than six million visitors since its opening. While it has found its audience, the project remains a notable example of financial and logistical complexity in public construction.