The icon of the Holy Trinity is a most important one for the Orthodox Church. In this icon, the fundamental truth of one God in three Divine Persons (the teaching on the Trinity) is revealed and acknowledged. According to St. Paul an many Church Father this belief is codified in the statement that we believe "in the Father through the Son and in the Holy Spirit"
In iconography, the Trinity is often depicted in the form of the Biblical scene of three angels appearing to Abraham by the oak of Mamre (Genesis 18:1-8). The icon is found on the iconostatis of our Cathedral. This image shows the first appearance of God to man and initiates the beginning of the promise of redemption. This if often referred to as the Old Testament Trinity.
The fulness of the revelation of the Trinity however takes place in the New Testament with the events associated with the incarnation of Jesus Christ and the various appearances of the Holy Spirit in the form of the dove. This thus is the New Testament Trinity as found in the exterior mosaic of the Cathedral. The mosaic depicts God the Father as the old and wise Father, and below him God the Holy Spirit in the form of a dove, and God the Son as the incarnate Christ the Teacher holding the Gospel with the first and last letters of the Greek alphabet: alpha and omega - "I am the beginning and the end". The icon shows clearly the unity of the three divine persons who are three, subject to their own Existence and Life, yet one in Divine Nature and being, one in Divine action and Will and one in Divine Knowledge and Love.
The mosaic depicts the Trinity in the spiritual world, yet a world that is attached to our universe. Christ is in fact stepping with His left foot on the world (the globe) proclaiming that He is truly the "king and ruler of the universe". Surrounding the Trinity on both sides are a series of eight angels who are know as the hosts of bodiless powers and serve the function of being the messengers of God. They are in fact the mediators between God in the Trinity and the world.
The mosaic as such illustrates in color a theology of the important teaching of the church on the Trinity. It is this same teaching that at each liturgy of the Orthodox Church is proclaimed with the singing or the recitation of the fourth century Nicean-Constantinopolian Creed - I believe in One God, in Three Divine Persons.
Holy Trinity Ukrainian Orthodox Cathedral is most honoured that Leo Mol, a widely known Ukrainian artist, accepted the commission of the mosaic of the Holy Trinity. The artwork was prepared in Winnipeg by Leo Mol, the mosaic stone was cut and executed in Rome, Italy by Marco Montecelli and Carlo Maloni and the final installation was done by Milano Tile Co. of Winnipeg, supervised by Alfredo Maida. (taken from the Celebration Program of the Millennium of Ukrainian Christianity and the Blessing of the Holy Trinity Mosaic - October 23, 1988)