The late baroque altar made of gilded bronze was presented in 1772 to king Stanislaus Augustus Poniatowski by Papal nuncio in the Polish-Lithuanian Commonwealth, Giuseppe Garampi, in the name of Pope Clement XIV. It was created in about 1772 in Rome and adorned with king's coat of arms in lower part and a relief with the scene of the "Beheading of St. John the Baptist" in the center. The central tondo is probably of an earlier production from about 1688-1689 by Urbano Bertesi after Ciro Ferri's design or was based on a 17th-century form. Similar bronze relief, commissioned in 1688 by Gregorio Carafa, Grand Master of the Order of Saint John preserved affixed to the front of the altar in the Oratory of St. John's Co-Cathedral in La Valletta, Malta.
In 1777, the king's altar was installed in the new Chapel of the Warsaw's Royal Castle, so-called Saxon Chapel (today's concert hall) and remained there until 1832, when all precious furnishings were taken to Saint Petersburg, possibly at the request of Joanna Grudzińska, Princess of Lovich, morganatic wife of the Grand Duke Constantine Pavlovich of Russia who died in Tsarskoye Selo in 1831. In aftermath of the November Uprising against the Russian Empire all furnishings of the Royal Castle in Warsaw were confiscated by order of Tsar Nicholas I and some destroyed like ceiling painting and the inscription on the frieze in the Knights' Hall and marble decorations of the Marble Room reused during conversion of the Piarists Church in Warsaw into Russian Orthodox Church.
The Poniatowski altar was installed in the church of St. John the Baptist in Tsarskoye Selo. In 1938 the church was closed by the Soviets and the altar was transferred to the Museum of the History of Religion in Saint Petersburg, then known as Leningrad.
Altar of king Stanislaus Augustus with Beheading of St. John the Baptist by Anonymous from Rome, ca. 1772, Museum of the History of Religion in Saint Petersburg.
Tondo with Beheading of St. John the Baptist by Urbano Bertesi after Ciro Ferri, 1688, St. John's Co-Cathedral in La Valletta.