The Royal Tenement House, located in the eastern frontage of the Lviv Market Square, is a former merchant's house that became the city residence of the Sobieski family and King John III in the 17th century. During the period of partitions, the house remained the centre of the Sobieski cult, and the memory of the ruler was the motive for transforming the building in the early 20th century into the King John III National Museum, the tradition of which is referred to by the contemporary Lviv Historical Museum.

A Short History of the Tenement House
The oldest parts of the Market Square building are the fifteenth-century cellars with stone portals and the walls of yellow and glazed brick preserved up to the height of the first floor. The current museum building was constructed in the second half of the 16th century using the walls of two adjoining older houses. One of them belonged to Melchior Haza, a merchant and patrician of Lviv. Part of the house was taken over from him in 1561 by Jerzy Gutteter (d. 1565), a merchant and Kraków councillor. His son Peter (d. 1572), on the other hand, sold the two-storey house in 1572 to the Greek merchant Konstantin Korniakt (c. 1520-1603), who after his ennoblement in 1571 leased royal duties from Ruthenian lands.

Reconstruction of the tenement house by the Korniakt family
. In 1577 Korniakt acquired the remaining parts of the Melchiorhazov tenement from the burgher of Kraków, Frederick Szmalcz. On the site of the partially demolished houses, Korniakt erected a building occupying two plots of land on the Market Square side, connected to the purchased back house on Blacharska (now Fedorowycza) Street. The date of completion of the reconstruction is assumed to be 1580, as can be seen in the finial of the gate portal from this street.

The author of the reconstruction of the house and the Renaissance façade may have been Petr Barbon (d. 1588), an associate of the Lviv architect Pavel Romany (d. 1618), who was also employed by Korniakt in the construction of the tower of the nearby Wallachian Church (1572-1580). The period of the Renaissance reconstruction includes internal portals and beamed ceilings in the market building, and a chamber in the back house with a beamed ceiling and Renaissance frieze. The figural attic with the figures of the king and royal guards holding shields with the Korniakts' coat of arms was created at the same time.

After Konstanty Korniakt's death in 1603, the building was given to his last surviving son, Konstanty Korniakt the Younger (1582-1624), who lived from the beginning of the 17th century in Bialoboki in the Przemyśl region. Korniakt the younger sold the family house in Lviv to the Monastery of the Discalced Carmelites in 1623, but died a year later during a Tatar invasion, which caused legal problems that lasted until the mid-1730s.

The tenement in the hands of the royal Sobieski family
In 1640 the tenement was bought from the monastery by Jakub Sobieski (1591-1646), at that time Voivode of Bełz, and after his death the building became the property of his widow, Teofila of Daniłowicz Sobieska (1607-1661), who managed the property, renting shops to merchants and city officials. The house was inherited by the future King Jan Sobieski, who often resided in the tenement. During the years of John III's reign, the cloisters in the courtyard, mostly removed in the 19th century, were extended.

The town house of the king also fulfilled a traditional commercial function: shops were rented to merchants, and the cellars were used to store honey from the monarch's apiaries. An element of the house decoration from this period is the cartouche with the Sobieski family coat of arms, Janina, placed in the portal from Blacharska Street. After Jan Sobieski's death, Maria Kazimiera occasionally lived in the tenement house. However, from 1698, Prince Alexander (1677-1714) stayed here regularly. That year, during an official visit to Lviv, the queen was visited in her town house by the newly elected King Augustus II the Strong (1670-1733). The Queen, upon leaving the Republic, issued instructions concerning the tenement house. She ordered that the property be kept in good condition and that rooms be made available to her brother and friendly aristocrats. During the subsequent division of the inheritance, concluded in 1699, the Lviv building was given to her middle son, Prince Alexander Sobieski, who continued to derive income from renting the commercial premises. When he died, in 1715, Prince Jacob relinquished to his youngest brother, Prince Konstantin, the half of the Royal Tenement House due to him after his brother. Konstanty Sobieski (1680-1726) owned the building until 1724, when he was forced to sell part of his property due to mounting debts.

City residence of the Rzewuski family
. The Lviv house was purchased by Stanisław Mateusz Rzewuski (1662-1728), field hetman of the Crown and starosta of Chełm. The Lviv tenement house remained in the hands of the Rzewuskis throughout the 18th century. Together with adjoining purchased houses, it became part of an extensive city residence where the hetman organised opera performances. Stanisław Mateusz Rzewuski died in his tenement house in 1728. The house was inherited by his eldest son, Seweryn Józef Rzewuski (1691-1754), Grand Referendary of the Crown, later Voivode of Volhynia. In 1731, the richly decorated Kamienica Królewska was the venue for the wedding celebrations of Seweryn Józef and Antonina Potocka, Grand Warden of the Crown. The bride and groom were ushered up the piano nobile via a ceremonial staircase through the cloisters of the courtyard. After the heirless death of Seweryn Józef, the tenement passed to his brother, Wacław Piotr Rzewuski (1706-1779), at that time field hetman of the Crown, who left an estate burdened with debts. His son, Józef Rzewuski (1739-1816), starosta of Drohobych and Nowosielec, and lieutenant-general of the Crown army, was forced to buy the tenement at public auction.

Restoration of the Royal Tenement House
At that time, the representative rooms already had the same layout and size as today, while the balcony in the front elevation did not yet exist, and the first floor was accessed by a wooden staircase from the hallway. The courtyard of the building was surrounded on three sides by arcaded galleries, and in the rear part there was a stone staircase covered with a roof.

The starost of Drohobycz collected a rich art collection in the Royal House, which included paintings, numismatic items and, above all, a library of 20,000 volumes.

In 1793, Jozef Rzewuski carried out a restoration of the townhouse, as evidenced by a plaque above the entrance to the royal rooms. Even then, he treated the building as a historical memento of King John III, hence the inscription AEDES OLIM IOANNIS III REGIS POLONIAE (The seat of the once King John III of Poland) on the second plaque. The staircase, the floors of some of the rooms or the stuccoed ceilings in the representative interiors were created during this time.

The starost of Drohobycz gradually indebted the building, recording the loans granted to him on his mortgage. In 1804. Józef Rzewuski sold the tenement house with all its furnishings and collections to his nephew, Aleksander Chodkiewicz (1776-1838), later a colonel in the army of the Duchy of Warsaw, general and senator of the Kingdom of Poland.