Lateran Council, First  Lateran Council, First, 1123, 9th
ecumenical council of the Roman Catholic Church, summoned by
Pope Calixtus II to signal the end of the investiture
controversy by confirming the Concordat of Worms (1122). It was
held in the Lateran Palace, Rome, making it the first council to
be held in Western Europe. Many of the council's decrees became
part of the evolving corpus of medieval Latin canon law.   More
on Lateran Council First from Fact Monster: