EQUILATERAL TRIANGLE PLAN IN EUROPEAN CHURCH ARCHITECTURE J. KRZYSZTOF LENARTOWICZ Abstract: The paper presents design projects and buildings based on the equilateral triangle plan. The author has identified about 40 churches of this kind in Europe, dated from the 12 th to the 20 th centuries. From geometric point of view, three axes are the minimum to obtain a centralized plan, which fascinated many architects- mathematicians of the late Renaissance. From functional point of view, such a plan is inconvenient, as the converging V-shaped interior corners are extremely difficult to be arranged. From the point of view of building materials and construction techniques, wedge-shaped exterior corners are sensitive places and such edges are hard to be produced. The paper discusses several ways of ‘blunting’ the corners, worked out to avoid functional and technical problems. The main reason for applying such a difficult centralized plan is metaphysical in its nature. A significant number of buildings set on triangular plans are The Holy Trinity churches and chapels, their patrocinium having been adequately symbolized in visible form. References to the Holy Trinity, especially in Eastern Europe, might have been an important demonstration in the theological dispute between the Roman-Catholic and the Orthodox Churches about the Filioque. SYMMETRY IN ARCHITECTURE Symmetry plays an essential role in architecture: not only as organizational aesthetic principle of the space, but also as bearer of symbolic connotations. It is symmetry that conveys a sense of monumentality to buildings. This concerns the visual aspect of the building’s solid mass and elevation view. The functional solution does not require symmetry; in fact, in most cases, it contradicts symmetry. Inside large buildings the usage of rooms on one side does not correspond to that on the other side, although the building’s layout on the two sides may have been mirrored. The longitudinal symmetry axis of the building’s main body, utilized in its functional purpose, is important inside churches of Christian denominations, since it is the route leading from the entrance to the main altar. As a matter of principle this axis is then East-oriented. 1. THE CENTRALIZED PLAN The multiaxial symmetry has a specific meaning in architecture. It results in a centralized plan, the foundations of which are the symmetry axes that intersect at a single point. In the simplest case, 2 symmetry axes, intersecting at right angle, result in