The very first of the preserved buildings were Trinity Cathedral. It was built after the vision that occurred at the successor of Sergius of Radonezh, the Abbot Nikon. In 1422 in place of the wooden Church of the Serbian monks that found shelter in the monastery after the battle of Kosovo Polje, began the construction of the white-stone Church. The construction lasted three years, and following two years his painting.

Now Trinity Cathedral is a monument of early Moscow architecture and the continuation of the Vladimir-Suzdal architecture of the XIV-XV centuries. It is a modest little building that formed around the entire ensemble of the Trinity Sergius Lavra. The quadrangle of the temple like a cube with a slightly inwardly inclined walls, thus creating a sense of perspective. Outside the slope starts from the very bottom, and inside — from the arches of the portals that improves visibility. The plane of the facades are divided into three parts, ending in ogee-shaped arches — the Gables. High light drum located on the tetrahedral basis over the quadrangle, completed with a sparkling gold-plated helmet-shaped dome with the cross. Gold and covered with a multi-tiered roof of the Cathedral. Light drum off center to the side apses, in order to visually balance the structure. In addition, a large number of high window openings fill light iconostasis. Three apses of the Cathedral of equal height. The Central part of the altar stands a little stronger than the other.

Later, in 1548, to the Trinity Cathedral on the South side was added by Nikon the Church, as if Recalling regard, the Abbot with his teacher. A year earlier, the Abbot of the monastery of Saint Nikon was canonized, and over his grave was placed the temple. It is made in the Pskov style, which became popular in Moscow architects of the sixteenth century. In 1559, the same side of the temple there is another outbuilding – tent over the grave of Bishop Serapion. Thanks to all the annexes of the Cathedral began to look stacked.

Interior of the Trinity Cathedral served as the great Russian icon painter Andrei Rublev, invited Reverend Nikon, and Daniel Black. Unfortunately, the frescoes that time has survived. But the iconostasis came in its original form, with some modifications. The main temple icon "Holy Trinity" is now in the Tretyakov gallery, and a copy of it in the five-tier iconostasis of the Church of the Holy Trinity-St. Sergius Lavra together with other masterpieces of Russian painting letters of the monk Andrei Rublev. The artist founded the convent workshop of painters, in which he received lessons from many Russian masters of icon painting.

Trinity Cathedral daily receives pilgrims and tourists from all over the world who come to venerate the Holy relics of St. Sergius of Radonezh, who were buried here in a silver reliquary.

Trinity Cathedral, being the first stone Church of the Trinity-Sergius Lavra, keeping its main Shrine, became the Central building of the monastery. Here meet two main roads of the Trinity-Sergius Lavra, spreading in different directions and determining the layout. Annex, eventually surrounding the Trinity Cathedral, created a holistic architectural ensemble of the Cathedral, and the Church built on the monastery grounds, complemented his picture. Restoring the monastery in 1938, the architect V. I. Trofimov noticed that there proportion of the so-called "Golden section". It is observed in the height of buildings, and in the ratio of volumes. And removal of the buildings from each other is determined by the height of the Trinity Cathedral. For example, the Church of the Holy spirit is at the distance of two heights of the temple, and Cathedral of the assumption – three.