One of Austria's most important churches, St Stephen's Cathedral, contains the oldest Polish tombstone in Vienna. The tombstone of Bishop Alexander Mazowiecki, pastor of the Viennese church from 1442 to 1444, is preserved embedded in the wall in the northern nave of the cathedral, near the altar from Wiener Neustadt, to the left of the chancel.

Vladislav Jagiełło's nephew
. Alexander was born in 1400. He was the youngest, fifth son of Siemowit IV, Duke of Płock, and his wife Aleksandra Olgierdówna, sister of the Polish King Władysław Jagiełło. The future Tridentine bishop spent his childhood in Płock and, according to Długosz, in Wiskitki, where his parents solemnly received Jagiełło returning from the victorious battle of Grunwald. The chronicles also mention his frequent stays at the royal court. As the youngest son, he was destined for the clerical state from an early age, as evidenced by the title of parish priest of Gniezno, which was conferred on Aleksander by the king's efforts in 1414, after the death of Mikołaj Strosberg. After less than a year's stay at Jagiello's court, in 1417 Aleksander enrolled as a scholar at the University of Cracow. His years of study at the Faculty of Liberal Arts shaped the interests and views of the later Bishop of Trent.

The doctrine of conciliarism, i.e. the recognition of the universal council as the supreme authority in the Church, without the intermediation of the Pope, which was popular in 15th-century Europe and above all in the Krakow circle, became an idea that guided Alexander throughout the years of his reign. Despite failing to obtain a degree after graduation, he was elected rector of the university in 1422, which undoubtedly served to increase the university's external reputation. In the middle of 1423, Alexander took over the canonry of Gniezno from Zbigniew Oleśnicki and received the episcopal infula. At that time he did not yet hold higher orders, and this did not change until 17 February 1424, when, already a Tridentine elector, he was ordained by Pope Martin V.

Bishop of Trent
Alexander's nomination as Bishop of Trent appeared in the papal chancery as early as October 1423. Cymbarka of Mazovia, Alexander's sister, married in 1412 to Ernest I Zelazny of Innsbruck of the Habsburg dynasty, who were keen to fill the episcopal throne with their own relatives, may have been the first to propose his candidacy. Alexander was officially solemnly ordained bishop on 27 September 1425 by Henry Scarampi, bishop of Feltre, and after four years of Tridentine interregnum, caused by a dispute over the choice of candidate, he took the reign of Trent. Before this happened, however, after leaving his homeland in early 1424, Alexander of Mazovia travelled. One of the most important of these was a stay in Innsbruck, where the bishop-elect succeeded in concluding a settlement with Count Frederick IV, who had been engaged since 1419 in the aforementioned dispute with Martin V over the choice of a suitable candidate for bishop. The visit facilitated the then young Alexander's assumption of power in Trent.

From the very beginning, Alexander polonised the principality he governed. Against the wishes of the Habsburgs who were related to him and who wanted to maintain a real influence on the politics of Trent through the bishop, he sought to preserve the full, both external and internal independence of the small state 'organism'. Alexander entrusted almost all the most important positions of the state and ecclesiastical apparatus to Poles who, at his behest, wrote down the new laws contained in the so-called 'Statute of Alexandria'. Among the Poles who arrived in Trent were Stanislaw Sobniowski, who was appointed chancellor of the duchy, Jan of Piertkow, the bishop's chaplain, and Paweł Włodkowic of Brudzenia, spokesman for Polish affairs at the Council of Constance in 1414 and former rector of the University of Cracow.

Such ostentatious favouritism towards his compatriots was met with incomprehension and rebellion from Tridentine society and dignitaries. Alexander suppressed the protests with the help of the army he had brought from Poland under Piotr Kunicki. Seeing resentment growing over the years and conspiracies involving the Habsburgs as well, the bishop, keen to consolidate his position, began a search for allies, which he finally succeeded in 1438, when the powerful Visconti family of Milan supported his rule in Trent.

Alexander ruled as Bishop of Trent for the rest of his life. Criticised and portrayed in the literature as impulsive, violent and uncompromising, Alexander of Mazovia faced, throughout his time as bishop, criticism from the Duchy of Tyrol and resentment from the Tridentine cities and vassals who wanted to deprive him of power at all costs.

Council of Basel
Alexander's summons to the deliberations of the Universal Council had already been made in 1432, but due to the continuing unrest in Trent, the bishop did not arrive in Basel, accompanied by Stanislaus Sobniowski, until 17 December 1433. The deliberations were imbued with the spirit of humanism developing in Italy at the time, and Alexander, bringing together both Italian and Polish dignitaries around his person, established a certain thread of cultural understanding between the nations and may have indirectly contributed to the later creation of humanist ideas in Poland.

The later years of the Basel meeting proved to be a turning point in Aleksander Mazowiecki's life, when, in the ongoing dispute between Pope Eugene IV and Felix V - the pope elected by the Council and therefore an antipope - the bishop, faithful to the idea of conciliarism, supported the latter without hesitation. This brought Alexander a great deal of recognition and proposals, thanks to which he became successively patriarch of Aquileia (1439), titular cardinal of St Lawrence "in Damaso", bishop of Chur (1442), and pastor of St Stephen's Church in Vienna (1442). The election of Felix V to the throne started the Basel schism, which lasted until 1449. During this period, there were frequent disputes over support among European rulers, and Alexander, a loyal supporter of Felix V, was sent by the council in the role of bishop-diplomat on missions as an effective mediator of all clashes and tensions.

Vienna - the last years of Alexander Mazowiecki's life
Bishop Alexander Mazowiecki spent the last two years of his life in Vienna, where, in the shadow of the growing Turkish threat, as pastor of St. Stephen's Church, he tended to concentrate on enjoying the riches and privileges then present in his new and last place of residence. At the end of May 1444, Alexander fell ill and, although there was initially no indication that the prognosis might be bad, his condition suddenly deteriorated. On the second of June, surrounded by close associates, Alexander Mazowiecki died. The funeral took place on 4 June 1444 at St Stephen's Church. The tombstone, made of Salzburg red marble and set vertically into the wall of the north aisle, depicting a life-size Alexander dressed in a priestly robe is still preserved in the cathedral today. Its founder was probably Emperor Frederick III, the bishop's nephew, who may have been advised on the foundation by the imperial secretary Enea Silvio Piccolomini, later Pope Pius II, who maintained good relations with Alexander during his less than two-year stay in Vienna. It is in Piccolomini's letters that references to Alexander Mazowiecki's illness and the day of his death have been preserved.

The marble slab shows a bas-relief figure of the bishop, dressed in a long priestly robe and a cardinal's almation, holding a large cross in his left hand and showing a sign of blessing with his right. On Alexander's robe are carved four shields of arms, two of which depict the Piast Mazovian eagle, and another, presumably an eagle alluding in some way to the Viennese prebend, although this symbolism has not been confirmed.

On the slab, around the figure of Alexander, is carved an inscription in Gothic minuscule, consisting of the date of death and the dignities which the bishop held during his lifetime. Missing from among these, however, is an indication of the position of pastor that Alexander held at St Stephen's Church in Vienna, which naturally entitled him to be buried in the church. In an iconographic study of the plate in question, Professor Szczęsny Detloff pointed out that the information about this title was hidden in the words 'et Illustris Princeps', which cannot refer to Alexander's princely origin, as this was expressed in the fragment 'D ux Mazovie'. Nor does the passage in question indicate his episcopal dignity in the Duchy of Trent, where Alexander was formally a member of the episcopal capital ('administrator Ecclesie tridentine'). It should also be mentioned that, since the foundation of St Stephen's Church by Archduke Rudolf IV, the title of prince may have been used by resident prelates who also held the privilege of pontificate, which would also indicate the inclusion of the title of parish priest in Alexander's plate in the above-mentioned words 'et Illustris Princeps'.

The provenance and workshop responsible for the creation of the tombstone, although discussed in the literature, has not been accurately indicated or confirmed. The creation of the carved slab was most likely commissioned to an artist working in the area between Bressanone and Passava, where the naturalistic trend, symmetry and frontal carving of imagined figures were popular in the first half of the 15th century, and examples of this type of tombstone are still preserved in churches there today. Also relevant to the recognition of Passava as the place where the slab may have been created is the fact of Piccolomini's visit to the bishop there a month after Alexander's death. During his stay with Leonhard von Laiming, the imperial secretary viewed the then-completed tombstone of the Passava bishop in the cathedral, which he later mentioned in letters. Piccolomini's acquaintance with the Passava sculptural design may have been the inspiration for the foundation of the Alexander Mazovian tombstone.