The Series Historic Buildings in Transylvania, launched in 1993, presents the most precious examples of Transylvanian built heritage connected to the Hungarian culture, with the purpose of drawing the general public's attention on values, heritage and our responsibilities towards these. The publications of this series are recommended especially to those who at present own or use such values, but also to those who are interested in history, architecture and the Transylvanian art.

Number 25 of the Series Historic Buildings in Transylvania presents the Calvinist Church of Oradea–Olosig. The current town quarter was originally an independent settlement named Villa Latinorum Waradiensium, inhabited by the Vallon population that was established here by the Bishop of Oradea in the 11^th-12^th centuries. Due to the artisan and merchant strata settled in the 16^th century, the settlement developed rapidly. The construction of the Protestant hall church, originally without a tower, was started in 1784, soon after the Edict of Tolerance came into force in 1781, the first service taking place in 1787. The Eclectic, two-story tower was attached to the Baroque western elevation in 1884. Besides the tasteful Empire furnishing, the valuable embroidered tablecloth of Princess Zsuzsanna Lorántffy, dating from 1635, is also worth mentioning.