Mainstream classical scholarship has long considered as lost a Roman “historical” relief, excavated in the earlier part of the 18th c. in the Palace of Domitian on the Palatine hill. Showing an emperor sacrificing, it is known as the Nollekens Relief after Joseph Nollekens, an accomplished British sculptor who came to possess it in the 18th c. Besides being a sculptor and painter, he was a sculptural restorer and dealer active between 1761 and 1770 in Rome, where he worked in the workshop of the sculptural restorer Bartholomeo Cavaceppi and in his own studio. The relief has been known chiefly from two engravings and a pen-and-watercolor drawing, all produced in the 18th c., but, rather than being lost, the relief has been hiding in plain sight in the Gatchina Palace near St. Petersburg. Its dimensions are 88 cm high x 139 cm wide. A recent visit to St. Petersburg established that the relief has been continuously in the Gatchina Palace since the late 1770s and that it had been damaged not only in antiquity but also during and after World War II. I also discovered that a cast of it existed by 1870 and that a photograph of the relief itself had appeared in an obscure Russian publication of 1914.