The last king of Poland, Stanislaw August Poniatowski, following his abdication and the death of Tsarina Catherine II, was...invited to St Petersburg by her son and successor, Paul I. The monarch spent the last months of his life in the Russian capital, at the imperial court. He ended his life on 1 (12) February 1798 at his St Petersburg residence, the Marble Palace. His final resting place for 140 years was the crypt in the Church of St Catherine of Alexandria on Nevsky Prospekt.

Royal burial
Tsar Paul I ordered a funeral ceremony worthy of a crowned head. The body of the deceased was embalmed. The Russian emperor personally placed a golden crown, made in Moscow especially for the occasion, on the deceased's head. A four-week mourning period was declared, and on 5 March the body was transferred from the palace to St Catherine's Church. The author of the decoration of the church and the catafalque was the architect Vincenzo Brenna. Józef Kozłowski's requiem in E flat minor, 'Missa pro defunctis', was sounded during the three-day ceremony. The coffin was lowered into the crypt, which was covered by a stone slab with the inscription:

STANISLAUS AUGUSTUS/ REX POLONIAE MAGNUS DUX LITHUANIAE/ INSIGNE DOCUMENTUM UTRIUSQUE FORTUNAE/ PROSPERAM SAPIENTER DIVERSAM FORTITER TULIT/ OBIIT PETROPOLI KAL. FEBR. MDCCXCVIII./ NATUS ANNOS LXVI/ PAULUS I AUTOCRATOR/ ET IMPERATOR TOTIUS RUSSIAE/ AMICO ET HOSPITI/ POSUIT

[Stanislaw August/ King of Poland Grand Duke of Lithuania/ an eloquent example of the vicissitudes of fate/ auspicious reasonably, adversity valiantly endured/ Died in St. Petersburg on 1 February 1798/ in his 66th year/ Paul I Autocrat/ and Emperor of All-Russia/ to a friend and guest/ laid down.]

The inscription was soon obliterated. In 1821, a new plaque with an amended text was placed, funded by the Metropolitan of Mogilev, Archbishop Stanislav Siestrzencewicz. In time, still in the 19th century, the slab was replaced again, restoring the original inscription. A fragment of the latter panel has been preserved to this day.

20th-century fate of the royal remains
In 1938, the Polish Consulate in Leningrad was notified of the closure of St Catherine's Church and the possibility of taking away the royal remains. The post was obliged to arrange the formalities of taking the historic coffin from the crypt and shipping it to Poland. The consuls completed all the necessary procedures: the commission opening the crypt, placing the remains in new coffins, metal and wooden, sealing, ceremonial farewell in the temple and transport to the railway station. Two secret reports dated 27 June and 5 July 1938, signed by the Polish consul Eugeniusz Weesego, have been preserved in this regard, from which we learn, among other things, that "... the royal remains, together with the lower part of the original coffin, were placed in a metal box, after which a sanitary and customs inspection was carried out. It was found that the royal crown was perfectly preserved; tests carried out on the spot with sulphuric acid indicate that it is a crown of gold. The Soviet representatives therefore asked for additional information as to whether this crown could be sent to Poland. After telephone communication with Moscow, a positive answer came. The crown was placed at the head of the coffin. Upon examination of the remains, it was found that only ashes remained of the body and bones, and only matter and brocades had been preserved. This is to be explained by the fact that during the floods which took place in the meantime, the church vaults were flooded with water, which accelerated the process of decomposition of the body and bones...".

The lead coffin with the remains of Stanislaw August and two urns containing the king's heart and viscera were sent to his birthplace, Wołczyn near Brest (Polesie voivodeship), and deposited in the church crypt. After 17 September 1939, the grave of Stanisław August was once again within the borders of the USSR. In 1995, the coffin with the remains of the royal burial brought from Belarus was laid to rest in the vaults of the Warsaw Archcathedral.

Restoration and conservation works in the crypt
Meanwhile, in St Petersburg, during the reconstruction of St Catherine's Church in the 1990s, the royal crypt was also tackled. After the removal of an 80-centimetre layer of rubble, what remained was an empty basement and above it - a damaged inscription plate in the church floor. The group of Russian conservators was led for several years by Dr Romualda Hankowska, an art historian and conservationist. Thanks to her research in the archives of Moscow and St Petersburg, hitherto unknown materials have come to light, including On the Burial of King Stanislaus of Poland in St Petersburg and The Registry of Things Taken to Dress His Majesty after His Death in February 1798. The latter document states what the King wore after his death. It also clarifies the issue of orders. It does not confirm, as many studies do, that the King was buried with the Order of the White Eagle, but mentions two Russian orders: St Andrew's and St Alexander Nevsky.

Works in the crypt included: cleaning the walls and vault, drying the room, installing a grille at the entrance and installing lighting. In order to separate the original royal crypt, a decorative grating with a shield with a gilded royal monogram was set in place of the former partition wall. Behind it, a surviving fragment of the inscription panel was placed. A marble information board, in Polish and Russian, was placed in the church.

In time, a portrait of Stanislaw August painted by Professor Wojciech Kurpik of the Warsaw Academy of Fine Arts was hung in the crypt, and a small exhibition devoted to the king and his final resting place was arranged. In the sanctuary, at the entrance to the sacristy, a replica of the historic slab was installed in 2018 in a hole in the floor that had been covered temporarily for years.

Also deposited in the basement of St Catherine's Church is a coffin containing several anklets of King Stanislaw Leszczynski, taken from Nancy to Warsaw after the French Revolution and given to the Society of Friends of Science. Looted by the Russians after the November Uprising, they ended up in the Imperial Public Library in St Petersburg. Thanks to the efforts of the Polish community, they were deposited in the royal crypt in 1857. They were returned to Poland in 1922. Such was the tragic fate of the two Stanislaus monarchs who died in exile - according to legend - supposedly because they were crowned in Warsaw rather than Wawel.