One of the oldest beeches in Poland, called “Sobieski” (trunk circumference 732 cm), growing on the Rybnicki Plateau on private property in Świerklany Dolne, was studied as part of a project entitled “Documentation, Analysis and Landscape Design”. Research on the tree’s condition began in 2009. In 2017 a sample from a broken bough was taken for dendrological analysis. In 2018 the condition of the trunk condition was evaluated using a PiCUS tomograph. Study of forest areas in the middle part of the Rybnicki Mesoregion revealed the presence of a group of magnificent beeches. The Jankowicki Forest complex is 2 km away from the “Sobieski” tree, so a genetic relationship is highly probable. Gene samples were taken to assess the degree of genetic relationship or to find unique alleles characteristic for the tree monument. As the Moravian Gate is nearby, Czech studies on tree monuments in eastern Moravia were analysed. A search of archives focused on the historical links between “Sobieski” growing near the no longer extant Kundlauer Manor and the march of King John III Sobieski’s army through Upper Silesia in 1683.