The article is devoted to the study of the specifics of the development of the profane and sacred space of the Krylos mountain, on which in the middle of the XII century the main shrine of medieval Halych was built – the Dormition Cathedral, which was discovered by Yaroslav Pasternak. Attention is paid to the reasons for the arrangement of the cathedral on not the best place on the mountain with a noticeable northern slope. For this purpose, according to archeological sources, the condition of households and religious development of the area intended for the cathedral and the nearest territory before its construction was analyzed. It is established that the studied objects functioned in this area from VIII to the middle of the XII century. Under the central part of the cathedral, Ya. Pasternak discovered a large pit, which he interpreted as the remains of a pagan shrine. According to Yu. Lukomskyi, this object was used for firing plaster. Results of activity of the expedition led by V. Aulikh discovered two water drainage channels cut by the foundations of the northern wall of the cathedral was important to highlight the question of the construction site of the cathedral and the functions of this object. These channels arranged by stone constructions were probably used to drain water from the spring(s), and the large pit may have been the remains of a pagan shrine built nearby. It was only during the building of the foundations of the cathedral, in particular for the north wall, that the builders cut these drainage structures. Since then, these structures, like the sources, stopped functioning. This is confirmed by later chronicle descriptions of the military events of the ХІІІ century when those of its members who were hiding in the cathedral died of thirst without water. In the example of the Dormition Cathedral of medieval Halych, built on the place of ancient household and religious buildings of pagan times, we see that many Christian churches bear the seal of duality: the sacred in them is not completely separated from the profane. On the contrary, the sacred is often manifested through the profane, that is, the solemn – through the secular, mundane. Key words: Dormition Cathedral of medieval Halych, Krylos mountain, residential and household buildings, a pagan temple, profane and sacred space.