With the advance of the Ottoman Empire the Archiepiscopate of Esztergom was forced to leave its seat and move to Nagyszombat. The buildings of mediaeval origin on Castle Hill, first housing royalties and later the archbishop, were appropriated by the military forces and suffered considerable damage from sieges and the Ottoman domination. The rule of the Turks ceased in Esztergom in 1683, but the archbishopric did not return before 1820. Nonetheless, the archbishops of the 18th century were also preoccupied with the fate and future of the buildings on Castle Hill.

Archbishop Ferenc Barkóczy (1761–1765, fig. 4) commissioned the Vienna-based architect of French origin, Isidore Ganneval (1730–1786) to plan a centre of ecclesiastical management on Castle Hill. Unfortunately, it is hard to glean from the fragmentary archival sources what exactly Ganneval was asked to design. His extant survey drawings are only about the renaissance Bakócz chapel which survived the vicissitudes of the centuries relatively intact. Ganneval’s fairly modest fee and his stay of a few months only permit the assumption that he was contracted only to draw up a sketchy proposal. The wooden model (fig. 5) only known from a photograph and possibly perished by now, which can hardly be fitted among the subsequent plan variants, might as well reflect the ideas inspired by his planning work in Esztergom. The conception documented by the wooden mock-up does not take into account the existing, mostly ramshackle buildings and fortifications. The “Navis Ecclesiae” idea represented by the model shows the cathedral flanked by wings of the archiepiscopal palace, the buildings of the theological college are situated lower, and the main road to Visegrád is lined by the canons’ houses. The sanctuary of the cathedral faces west breaking with the tradition of the eastern apse. The groundplan is a fusion of centralized and longitudinal plans, its basic element is the Bakócz Chapel (fig. 6) the mass of which is reiterated and enlarged in it.

This proposal ignored the possibility of preserving the mostly mediaeval buildings and fortifications on Castle Hill. In December 1761, however, Archbishop Barkóczy was compelled to sign the obligation by the War Council to undertake the maintenance of the Castle Hill fortifications and in case of enemy attacks to accommodate imperial troops there. It was only through the intervention of the Queen, Maria Theresa, that Barkóczy could be exempted from this obligation in 1763.

The next plan of a church administration centre was elaborated by Franz Anton Hillebrandt (1719–1797) whose first plan series was made during the validity of the military obligation from December 1761 to March 1763. It is quite possible that the style of the architect of the Hungarian royal chamber was closer to the taste of the baroque art patron Barkóczy than that of Canneval twenty years his junior, representing the progressivity of revolutionary architecture. The latter was also commissioned by Anton Christoph Migazzi to design the cathedral of Vác, whose style did not attract followers in Hungary.

Apart from the principal plan known in the copy by Anton Hartmann (fig. 7) only four pieces of the first plan series survive, including the first floor plan of the seminary building (fig. 8). This baroque conception keeps the fortified walls and bastions around Castle Hill but demolishes the military buildings on the plateau (barracks, hospital, stalls, etc.). It is like an architectural counter-proposal to Ganneval’s wooden model, taking into greater consideration the relief features than the perfunctory mock-up. Hillebrandt delivered these plans to Archbishop Barkóczy on 10 March 1763 and forwarded the queen’s message at the same time: the financial obligation to maintain the military defences of Castle Hill had been abrogated. It immediately invalidated the plans just presented, and obstacles from the path of planning were removed. That was probably the stimulus behind the free-handed amateur linear drawing of a groundplan made perhaps by the archbishop or his representative for the architect in 1763 (fig. 9) in which the functions of the buildings are defined. In a sense it returns to Ganneval’s model which handled Castle Hill without any restrictions.

Only few – a mere six sheets – of Hillebrandt’s plans are known from after the sketch. (A part of the plans were probably taken by architect István Möller to Budapest in the first decades of the 20th century and possibly perished during the siege of the capital in 1945 or during the reconstruction.) Anyway, it must have been on the basis of this second series of plans that the demolition of mediaeval remains, soil levelling and the laying of foundations began in 1763. In 1764, the collapse of an Ottoman minaret built using a mediaeval stair-tower caused the crushing of Porta Speciosa, the main portal of the mediaeval St Adalbert cathedral. Mainly preparatory construction went on until the death of Archbishop Barkóczy in 1765. That interrupted the building of a baroque church administration centre for good.

Building commissioner János Máthes (1785–1848) summed up in his work published in 1827 how far the construction had arrived and what was built later. Maria Theresa requested Hillebrandt to plan a church dedicated to King Saint Stephen for the garrison reinstated on Castle Hill, which was constructed in 1767–1770. It was – on a smaller scale – on the site of the planned baroque cathedral, certainly not using its foundation walls. About the situation a layout drawing (fig. 12), groundplan and design plan (fig. 13) are included in Máthes’s book. In addition, a now latent or extinct, mock-up (fig. 14) made by Máthes also reflects the situation on Castle Hill in the last quarter of the 18th century. In the lower part of the model made in the early 1820s groundplans of the buildings on Castle Hill could be seen (fig. 16). One of the specialties of the church was the copy of the Hungarian royal crown placed on the spire as the crowning ornament. On the façade on top of the stairs adjacent to the broad ramp leading to the basilica of today the statues of Saints Stephen and Ladislaus carved by the Pest sculptor József Hebenstreit were erected. Surviving items include side altar pictures painted by Anton Karl Rosier of Pozsony which are today in the Esztergom church of the Sisters of Mercy of Szatmár. The later rebuilt garrison church was pulled down in 1821 to make room for today’s cathedral. One of the first moves of the new construction was the transfer of the Bakócz Chapel to its present place. The cathedral, the construction of which started on plans by Pál Kühnel (1765–1824) and János Packh (1796–1839) fitted into a conception of a church government centre the model for which might have been provided by Ganneval’s plan of nearly sixty years before.