ENan Expression of Open Unity in Baroque Church Ensembles of the Grand Duchy of Lithuania The article explores the principle of bilateral symmetry and its expression in Baroque architecture. The symmetrical composition is linked to the fundamental artistic principles of the Baroque and it is argued that symmetry became the new architectural norm, replacing Renaissance harmony. The axis of symmetry is analysed as an expression of Baroque contradictory harmony, with its qualities of open unity. The axis in the Baroque becomes a physical and symbolic axis of movement. In the second part of the article, the theoretical propositions are analysed in the examples of Baroque churches of the Grand Duchy of Lithuania. A distinction is made between closed and open symmetrical ensembles. Different fields of meaning acquired by the axis of symmetry are recognized. The axis of symmetry in Baroque architecture is associated with contradictory qualities of unity and openness, which take their most pronounced forms in the period of Late Baroque. [From the publication]