The Baroque church of the Holy Trinity or commonly known as the Premonstratensian church was the site of the martyrdom of three saints in 1619. It the Middle Ages, the Royal House (a seat of the Royal Chamber), stood on the site of the present church. In 1618, at the beginning of the Counter-Reformation and the start of the Thirty Year War, The captain of the city established there a dwelling and a chapel for Jesuits in the Protestant town. Two Jesuits Melicher Grodecký, Štefan Pongrác were sent there, to work with a canon Marek Križin. On 7 September 1619, the forces of George I Rákóczi, the father of the Prince of Transylvania George II Rákóczi, stormed the castle and arrested the priests. They gave them a death sentence on charges of treason; accusing them of inviting the Polish army into Kassa. They were tortured and then beheaded that day. The execution of the priests shocked the local population, Catholics and Protestants alike.
In 1657, the Bishop of Eger, Benedict Kishdy, founded the first Košice University (Universitas Cassoviensis) close to the site. Later, the daughter-in-law of George I Rákóczi, Sofia Bathory, wife of George II Rákóczi, bought the ruins of the former Royal House with intention of building a church for the Jesuits there to make amends for the events of the Thirty Years' War. In 1681, construction on the church finished and it was opened.
On 21 July 1773, the Jesuits was expelled from the city as part of the suppression of the Society of Jesus. So in 1811, the church was given to Premonstratensians who currently administer the church.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.