UPPER ROOM of Jerusalem. – A Gothic-style hall within the Muslim mosque called Nebi Dā'ūd ("the Prophet David"), to the southwest of Jerusalem, outside the present walls, on the hill known as Sion. This mosque has two floors; on the lower floor, to which no non-Muslim may have access, the followers of Islam venerate the tomb of David. The upper floor comprises two sections; in the western part of the hall, Christians today venerate the place of the institution of the Eucharist, while in the smaller, eastern part, inaccessible to them, they venerate the place of the descent of the Holy Spirit at Pentecost.
It is still debated whether this is the same place where Jesus instituted the Eucharist, where the Risen One appeared several times, and where the outpouring of the Holy Spirit took place. From the earliest Christian centuries, a small church stood on Mount Sion called "of the Apostles"; 4th-century writers attest that the descent of the Holy Spirit was venerated there, while they remain silent about the institution of the Eucharist. Thus St. Cyril, Bishop of Jerusalem (Cateches., 16: D. Baldi, *Enchiridion Locorum Sanctorum*, Jerusalem 1935, no. 370, p. 602), the *Peregrinatio Aetheriae* (D. Baldi, op. cit., no. 732, pp. 603–605), and St. Epiphanius (De mensuris et ponderibus, 14: D. Baldi, op. cit., no. 733, pp. 605–607). The New Testament texts are not decisive. Mk 14:15 and Lk 22:12 refer to the room of the institution of the Eucharist as ἀνάγαῖον (= upper part of the house, upper room). When the Apostles returned to Jerusalem after the Ascension, they went up to τὸ ὑπερῷον, which also means "upper room." The Vulgate uses *coenaculum* in both places. In the same place, the Risen Jesus appeared to the Apostles, they elected St. Matthias, and received the Holy Spirit (Acts 1:15–26; 2). While these texts do not prove the identity of the room, neither do they prove that it was a different room. On the other hand, witnesses from tradition as early as the 4th century affirm that the memory of the institution of the Eucharist was also celebrated in this church: the *Didascalia of Addai* (D. Baldi, op. cit., no. 733, p. 606, note 2), and St. Jerome’s Epistle 53 (D. Baldi, op. cit., no. 734, p. 607). From the 5th century onward, testimonies in favor of this identification continually increase. Moreover, pilgrims recount that in the church of Sion, the house of Mary, mother of John Mark, was also venerated; others saw there also the house of James; the pillar of the scourging was venerated there, and from 415 the body of St. Stephen rested there. The house of the Evangelist St. John and the place where the Virgin Mary died were also placed on Sion. The original small church, around the year 400, was transformed into a great basilica, which various writers called by different names: "House of God," "Holy Sion," "Mother of all Churches." This basilica suffered greatly from the Persian invasion (614) and in 966 was burned by Jews and Muslims, but it was rebuilt as a double church by the Crusaders. This was destroyed in 1219. Around 1335, King Robert of Naples obtained the Upper Room from the Sultan of Egypt for the Catholic Church; and his wife, the pious Queen Sancia, built a convent next to it for the Friars Minor. But in 1552, they were expelled and the Upper Room reduced to a mosque. Only in March 1936 were they able to return beside it, where they built a small convent and a small church.