A Catholic-Orthodox village cemetery, established in the mid-19th century, has been preserved in Olszewo. It is located on the northern side of the village, at the edge of the development. The cemetery is dominated by modern Orthodox tombstones. According to the authors of the study (see bibliography), "the only interesting object [...] is the tombstone of Major of the 13th Ulan Regiment and commander of the 23rd Brigade of the Home Army Marian Ostrog-Kisielewicz, murdered by Soviet partisans and buried here in the presence of the entire local population in June 1944 г. The grave, in a metal fence, is located a few dozen metres to the left of the cemetery entrance. It is a horizontal slab made of granite with an oval concave inscription plaque". The preserved inscription reads: S. P. / MARIAN OSTRÓG KISIELEWICZ MAJOR 13-go PULKU ULANÓW / UR. 26 IX 1913 / DIED DEFENDING THE HOMELAND / 21 VI 1944. / MAY THE ETERNAL LIGHT SHINE UPON HIM //. Compiled from published information about the cemetery (see bibliography)