The history of humanity is full of lost things, sometimes relegated to oblivion, or destroyed by man or the erosion of time. Some of these disparate objects, real or imaginary, are collected and inventoried in this book: the enigmatic fragments that have survived from Sappho's poems, the Palace of the Republic in Berlin, the Caspian tiger, or the supposed skeleton of a unicorn. A captivating and unclassifiable work that gives us the opportunity to reflect on the meaning of loss and the role of memory through the evocation of twelve treasures that the world has lost forever, but which, thanks to the traces they left behind in history, literature, and the imagination, have a second life.