Not a classic escape room but a museum-wide treasure hunt that Sherlocked organized at the Rijksmuseum in summers 2018 and 2019. In The Secret Formula, teams hunted for a missing page from an 18th-century book by magician Cagliostro throughout the collection; the 2019 edition revolved around a secret society in the museum, with librarian Bert (including a chatbot version) as guide and museum staff playing as actors. With over 10,000 visitors in nine weeks and an average player rating of 9.4, it was a smashing success, especially among families and young adults. Visitors found the puzzles themselves mild—more of a treasure hunt than an escape room—but the setting among genuine masterpieces made up for it. The game was temporary and has definitively ended.