The painting, set in the late afternoon of May 3, 1791, shows the procession of deputies from the Royal Castle (background), where the Constitution has just been adopted by the Great Sejm, to St. John's Collegiate Church (left, now an archcathedral), where a Te Deum will be sung.
The procession moves down St. John's Street (ulica Świętojańska), surrounded by enthusiastic Warsaw residents and visitors.
The deputies are protected by soldiers.

While the procession was an actual historic event, Matejko took many artistic liberties, such as including persons who were not in fact present or had died earlier.
He did so because he intended the painting to be a synthesis of the final years of the Commonwealth.
He also felt that there was no real historic moment or location that fully captured the spirit of the Constitution, and so he, the artist, needed to create such a moment.
The painting, set in the late afternoon of May 3, 1791, shows the procession of deputies from the Royal Castle (background), where the Constitution has just been adopted by the Great Sejm, to St. John's Collegiate Church (left, now an archcathedral), where a Te Deum will be sung. The procession moves down St. John's Street (ulica Świętojańska), surrounded by enthusiastic Warsaw residents and visitors. The deputies are protected by soldiers.
While the procession was an actual historic event, Matejko took many artistic liberties, such as including persons who were not in fact present or had died earlier. He did so because he intended the painting to be a synthesis of the final years of the Commonwealth. He also felt that there was no real historic moment or location that fully captured the spirit of the Constitution, and so he, the artist, needed to create such a moment.
Constitution of May 3, 1791 (painting)