The Apostolic Palace is the official residence of the Pope which is located in Vatican City. It is also known as the Sacred Palace, the Papal Palace and the Palace of the Vatican. The Vatican itself refers to the building as the Palace of Sixtus V in honour of Pope Sixtus V.
The palace is more accurately a series of self-contained buildings within the well-recognised outer structure which is arranged around the Courtyard of Sixtus V (Cortile de Sisto V). It is located North-East of St Peters Basilica and adjacent to the Bastion of Nicholas V and Palace of Gregory XIII.
Rather than a "traditional" palace (a residential building surrounded by support buildings) the Apostolic Palace houses both residential apartments and support offices of various functions as well as administrative offices not focused on the life and functions of the Pope himself.
The building contains the Papal Apartments, various government offices of the Roman Catholic Church and the Holy See, private and public chapels, Vatican Museums and the Vatican library, including the Borgia Apartment now used to house artworks.
The ancient Vatican Palace had fallen into disrepair during the period of the Avignon Papacy, when the popes did not reside in Rome. In 1436 the Spanish traveller Pedro Tafur found it still in poor condition: "The Pope's dwelling is a mediocre place and when I was there it was ill-kept. Construction of the palace began on 30 April 1589 under Pope Sixtus V and its various intrinsic parts completed by later successors, Pope Urban VII, Pope Innocent XI and Pope Clement VIII.
In the 15th century, the Apostolic palace was placed under the authority of the prefect of the Apostolic palace. This position of Apostolic prefect lasted from the 15th century till the 1800s, when the Papal States fell into economic difficulties. In 1824, when this post was reviewed to save money, Leo XII created a committee to administer the palace.
The term Apostolic Palace has been used in other contexts not directly related to the actual Palace of Sixtus V.
It has been used, for example, as a general reference to the papacy itself in the same way the term "White House" is used to describe the United States Presidential administration generally, rather than the physical building itself.
The term was also referenced in the video game Civilization IV: Beyond the Sword, where a player could establish an Apostolic Palace as the symbolic "home" of a civilization's state religion. While the game's developers did represent the Apostolic Palace function with an image of St. Peter's Square (adjacent to the Apostolic Palace) the image, somewhat ironically, does not actually include a view of the Palace itself. Regardless, the in-game function of the Apostolic Palace is not religion-specific and the use of the term is representative of religious administration generally, rather than a specific reference to the Vatican.