Buda in the Turkish Era
Ferdinand could not accept the loss of the Hungarian capital, so in the summer of 1542 he set out with a huge army - under the command of the Prince of Brandenburg, Joachim - to reoccupy it. Hungarian troops also joined this army led by Péter Perényi and Miklós Zrínyi. However, by the end of September, 1542 the united army had only managed to lay siege to Pest, and shortly after this at the beginning of October they withdrew in failure. From this time on there was no siege for 56 years, so a "peaceful development" - i.e. the assimilation of Buda into the Turkish military and administration system - started.
There were Hungarian and other Christian citizens in Buda following the departure of the Queen's court and after part of the bourgeoisie had fled. 
These citizens had a certain autonomy, but they were subordinated to the Turkish, Islamic administration system. (The elements of the local government were organised on the basis of religious rather than ethnic groups. Although at first the Italians had their separate prefect.) The sultan appointed István Werboczy, the former chancellor, as chief judge of the local Hungarian citizens, but he died in October, 1541. He was said to have been poisoned by the Pasha of Buda. In the first year of the Turkish occupation the judge of the town remained the same person who had held this office before the conquest, and the representatives of the council were chosen from among the former elite. Turncoats can be found among the later judges of Buda, who were given the title of spahi for their services. According to the first known Turkish tax register of 1547 there were 238 western Christian (as the Turks saw them, faithless, that is kyafir, otherwise pronounced jaur) families in the town. The Christians were allowed to practise their religion "without restrictions" for a while, and the former Hungarian parish, standing in the northern part of the town, was left for them. It was the Church of Mary Magdalene, the predecessor of the later Garrison church. Both the Catholic and the Calvinist denominations used the church. Later, probably in 1596, this church was taken over and converted into a djami. Later the number of Christian families decreased because the Turks prohibited them from moving into the town.
The Jews formed a significant colony in Buda. In 1547, for example, 75 families were registered. Some of them had come back, while others were newcomers. Later their numbers fluctuated, decreasing by the turn of the century, only to increase at the end of the Turkish era. They also had their own judge.
The third group making up the population of Buda was the community of the "Coptic", Kiptile people. They were mainly Greek Catholics. In 1547 there were 60 families. The majority of these may have come here before the Turkish conquest. Their numbers gradually increased over time, since there were a lot of Balkan Slav people among the defenders of the fortresses and office holders and their religion was more palatable to the Turks. Historical sources refer to several of their churches, but the locations of these have not yet been pinpointed.
In the era of the Turkish occupation the fourth, nevertheless dominant religious-social group in Buda was that of the Muslims, which included not only the Turks but also other Muslim nationalities, and those who had converted to Islam, such as the Balkan Slavs. In the beginning they formed part of the defenders and officials, but later their numbers increased as family members joined them. Their significance is shown by the fact that they occupied all the former Christian churches and converted almost all of them into their own shrines. In addition to this they built a new church in one of the palace courtyards.
The town structure, network of streets and squares of Buda in the Turkish era changed little if at all. The Turks referred to the former royal palace as ich kala (inner castle) or hisarpeche (citadel), while they called the town (the Castle quarter) orta hisar (middle castle). The units of these territories were not identified as streets and squares (although they used them) but as specific housing blocks, groups of houses and smaller town parts, called mehalle, which were usually structured around certain objects, such as the Turkish djamis.
These changes were apparent on the exterior view of the town, both on the buildings and in them. In churches the furnishing and ornaments were thrown out or plundered, and they were converted into djamis. 
The first to be used for this purpose was the Church of Our Lady: "the Turks converted it into a main mosque, the altar and the tombstones were thrown out and a lot of things were walled up." - reported the traveller Hans Dernschwam on the occasion of his visit in 1555. (Dernschwam had lived in Buda for a long time before the conquest, so he could properly compare the new conditions to the old ones.) The Turks called the new djami Büyük (Great) or Sultan Suleyman djami. Later, being the oldest one, it was referred to as Eski - Old - djami as well. The Virgin Mary's or in other words Saint John the Almoner's Chapel of the royal palace became the Seray (Palace) or Enderun (Inner) djami. St Sigismund Provostry became the Küchük (Small) djami, and the church of St. John of the Franciscan order became the Pasha djami. The St George's Chapel in the former St George's Square (today's Dísz tér) was called the Orta (Middle) djami. Derschwam gave a clear description of this, too: "Their other mosque is the church of St George, which was completely surrounded by buildings. The heathens walled up the high arched windows halfway up, building and attaching their stalls and cottages to the walls." The Dominican church of St Nicholas was first used as a storehouse for weapons, then as Hüsrev Pasha's djami. Finally the church of Mary Magdalene was converted into a Muslim shrine in 1596, and was called the Fetih or Fethiyye (Victory) djami to commemorate the Turk's victory at the battle of Mezokeresztes (26-28 October, 1596). Where feasible, the tower in front of the church was used as a minaret, and if this was not feasible - as for example in the case of the former Franciscan church, which was not at the church's façade - they built a new one. According to our present knowledge the Murad Pasha djami, situated at the western outer-ward of the former royal palace, then called the Yeni Mahalle (new quarter of the town), was newly built.
In the Hungarian royal palace there were basic functional changes in addition to the establishment of djamis. Apparently, only the first pasha of Buda, who was appointed by Sultan Suleyman, resided within its walls. In the beginning his successors lived somewhere out in the suburbs, only moving back at the end of the 16th century, but not to the royal palace. They moved into the town, to the area north of the former Franciscan church (today's Várszínház). The palace completely lost its former role. Its territory and buildings were used as barracks, storehouses and as a prison. Its leader was the dizdar (castle supervisor). The pasha sometimes used it for meetings, and certain legations also visited it.
Changes were striking at the dwelling-houses - and Dernschwam may again be utilised as a witness to this. Though it must be noted that his descriptions probably related to the years directly after the conquest, when the dwellers of the town were newcomers, and in the majority of cases soldiers and officials without families. 
"The houses collapse one after the other. There is no new construction; the dwellers merely seek a shelter from rain and snow. The great, spacious halls and rooms were divided up into numerous cells, with walls pieced together from stone, clay and wood, just like a stable. They did not need cellars, and so filled them with rubbish. Nobody is a lord or owner of their own house." Building surveys and excavations proved the existence of the above mentioned walls made of stone, clay and wood in several places. However, there are also examples of more sophisticated Turkish constructions and renovations, such as skillfully hewn out vaults. Some information is available about the use of cellars in the Turkish era from a Turkish traveller, Evlia Chelebi, who lived a century later. He wrote: "There is a cellar under every palace. During sieges they seek refuge from cannon fire by going underground." Later Derschwam talks about another typical Turkish architectural solution: "All the houses became pigsties; they were surrounded by so many other buildings that one can hardly recognise the gates and the big old coach entries. They built gutters and stalls in front of and to the side of the houses, in which the Turkish craftsmen sit and work in the street - according to Turkish customs." In any case, the look of the medieval towns started to resemble that of eastern towns, and especially that of Balkan towns conquered at an earlier date.