The ecumenical council refers to a conference of the theological experts and the ecclesiastical dignitaries convened to settle and discuss matters of the various practices of the church. It is also called the oecumenical council.
nicaea
According to the NY Times crossword, the answer is "Nicaea."
A. V. Kartashev has written: 'Vselenskie sobory' -- subject(s): Church history, Councils and synods, Ecumenical, Ecumenical Councils and synods, History
S. Herbert Scott has written: 'General councils and Anglican claims in the light of the Council of Ephesus' -- subject(s): Christian union, Council of Ephesus (431), Councils and synods, Ecumenical, Ecumenical Councils and synods, Popes, Primacy
Roman Catholic AnswerThe first Ecumenical Council of the Church was the First Council of Nicaea, which, unsurprisingly was held at Nicaea as Councils are named after the town or location where they are held.
Popes do not develop out of Councils, Pope call Ecumenical Counsels.
Norman P. Tanner has written: 'The Church in the later Middle Ages' 'Kent Heresy Proceedings 1511-1512' 'The church in late medieval Norwich, 1370-1532' -- subject(s): Catholic Church, Church history, History, Religious life and customs 'Was the church too democratic?' -- subject(s): Ecumenical Councils and synods, History 'Is the Church too Asian?' -- subject(s): Ecumenical Councils and synods, History 'The church in council' -- subject(s): History, Ecumenical Councils and synods, Church history
Joseph F. Kelly has written: 'The ecumenical councils of the Catholic Church' 'The problem of evil in the Western tradition'
Roman Catholic AnswerThere was no new "church of Trent". The Council of Trent was 19th of 21 general ecumenical councils of the Catholic Church, (not counting the Council of Jerusalem in the books of Acts): First Ecumenical Council: Nicaea I (325)Second Ecumenical Council: Constantinople I (381)Third Ecumenical Council: Ephesus (431)Fourth Ecumenical Council: Chalcedon (451)Fifth Ecumenical Council: Constantinople II (553)Sixth Ecumenical Council: Constantinople III (680-681)Seventh Ecumenical Council: Nicaea II (787)Eighth Ecumenical Council: Constantinople IV (869)Ninth Ecumenical Council: Lateran I (1123)Tenth Ecumenical Council: Lateran II (1139)Eleventh Ecumenical Council: Lateran III (1179)Twelfth Ecumenical Council: Lateran IV (1215)Thirteenth Ecumenical Council: Lyons I (1245)Fourteenth Ecumenical Council: Lyons II (1274)Fifteenth Ecumenical Council: Vienne (1311-1313)Sixteenth Ecumenical Council: Constance (1414-1418)Seventeenth Ecumenical Council: Basle/Ferrara/Florence (1431-1439)Eighteenth Ecumenical Council: Lateran V (1512-1517)Nineteenth Ecumenical Council: Trent (1545-1563)Twentieth Ecumenical Council: Vatican I (1869-1870)Twenty-first Ecumenical Council: Vatican II (1962-1965)All of these councils were councils called by the Holy Father and attended by as many bishops as he could get there. They were all guided by the Holy Spirit and approved by Rome so that their decisions are binding on all of Christ's Church. Each and everyone of them was called to deal with various heresies. Many of their decisions involved the first time a doctrine was actually "defined" for the simple reason that it was the first time it had seriously been called into question. There was no new church after Trent, just as there was no new church after Nicaea. Despite other opinions to the contrary, the Church of Rome was established by Christ and remained faithful to Him throughout the centuries. There is no "church of Trent".
The historical city of Nicea, where early Christian ecumenical councils were held, is in modern-day Turkey on the Marmara and is known by the name İznik.
Sorry, you are going to have to be a whole lot more specific, there have been 21 Ecumenical Councils who have discussed Church reform over the centuries, and innumerable local Councils, plus the Roman Curia.
Francis Dvornik has written: 'Czech contributions to the growth of the United States' -- subject(s): Czech Americans 'Histoire des conciles' -- subject(s): Councils and synods 'The Slavs' -- subject(s): Slavs, History 'Photian and Byzantine ecclesiastical studies' -- subject(s): Church history, Orthodox Eastern Church 'Byzantium and the Roman Primacy' -- subject(s): Relations, Popes, Orthodox Eastern Church, Catholic Church, Primacy 'The Slavs between East and West' -- subject(s): Civilization, Slavic, History, Slavic Civilization, Slavs 'The ecumenical councils' -- subject(s): Councils and synods, Ecumenical, Ecumenical Councils and synods 'Gli slavi' -- subject(s): Slavs, History
The two councils are the council of Nicaea and the council of Constantinople.