We have such a mention of the chronicler. During the conquering of Halych in 1219 by Mstislav Udatny in the Assumption cathedral the Hungarian king Koloman was closed there: “the God made the strengthening on the church of Assumption mistress of Our Lady who could not suffer the desecration over Her temple, and gave him (Koloman) into the hands of Mstislav”. This event took place, when prince Mstislav, had won the Hungarian war-lord Filya, entered to Halych: “And ran out then Uhrys on a vault of the church, and other rose on cordages, and their horses were caught. The strengthening was made on the church, but those shot, and stones were thrown on town people, languished there from thirst, because there was not water in the city. And when Mstislav arrived, they seemed to him and they were taken from the church”. Something similar happened in 1254, when prince Izyaslav was defended in Halych by Danylo - the son of Roman.
There are mentions about Halych Cathedral of the XIV-XVI-th centuries, but we do not know the exact date of the destruction of the Assumption cathedral. And the site of the main sacred object of princely Halych many centuries was unknown. Its ruins were searched in nowaday Halych, and on the high bank of the river Limnytsya, and in Krylos, in the place of the Assumption church. Very closely to the solution of the secret of the cathedral was the researcher Yosyp Pelensky, who in 1911 did trial excavations near the Assumption church in Krylos. But finally the sight was localized only on July, 25 in 1936 by the expedition of the Scientific society named after Taras Shevchenko, which from the benediction of the metropolitan Andrey Sheptitsky, a glorious archaeologist Yaroslav Pasternak led. Two years in succession the scientist mortgaged the reconnaissance trenches on the Krylos central place of the ancient city of Halych, and on the sunny July day of the year adopted higher became a sensational day, because the shovel of the worker of D. Mykhalchuk blundered upon the massive wall of the stone blocks. This was the first track of foundations of the ancient Assumption cathedral of princely Halych. The foundations were of sizes (32,5-37,5 metres) in sizes and one and a half meters width and somewhat smaller in length then Kyyevan temple of St. Sofiya. And for its riches of the decoration and spatial location it did not yield even to the most prominent sacred temples of that time. The foundation of the cathedral was expounded mainly from the rudely treated blocks of the limestone, and the walls were made of the blocks of alabaster and limestone. The numeral finds of architectural details and the sculptural decoration gave us the picture of the appearance of the majestic Halych cathedral. The entrances to the temple were decorated with the perspective portals, toothed frisians were used in the external decoration, half-column with caps, cornices (gzyms).
The inside of the Halych cathedral was also decorated no less parade and carefully thought out. The floor of the Assumption temple was made of the slabs of alabaster and sandstone in combination with ceramic tiles, decorated the images of reliefs of plants and fantastic animals. Judging from the fragments of the plaster and tracks of frescos, the temple had paintings inwardly. The dome of the cathedral and protuberant surfaces of vaults were covered with leaden steel metal, and the roof – by the red tiles. Probably, there was representing the appearance of Oranta in the temple of Assumtion.
In the half closed of the temple, during excavations in 1937, Yaroslav Pasternak found out a stone sarcophagus with the mortal remains of prince Yaroslav Osmomysl. Most workers of researches adhere to the idea, that the cathedral is built for reigning of Yaroslav Osmomysl to 1157 and bind this event with the creation in Halych of the independent metropolian. Ancient manuscripts which were saved to our days are Halych Gospel of 1144 and Dobrylove Gospel of 1164 that at the cathedral there was a library and the writing-workshop for copying of books and «School of Os'momysl» included cultural and educational complex which the old Rus chroniclers remembered about with the fascination and praise.
After the Mongol-Tatar invasion in 1241, when Danylo Halytsky began to build a new capital – city Kholm and a new cathedral of Yoan Zlotousty, the Assumption cathedral began to fade quickly. For the last time a chronicler remembers the temple in 1254, and in writing sources it appears at the beginning of the XIV-th century. The very substantial factor of complete desolation of the temple became after the destroying of the city, the diminishing in the XIV-XV-th centuries of urban population which little facilities to retain this monumental building in the proper state. And after a decree in 1455, which was declared by the Polish king Kazymyr IV, it was forbidden to build and to repair and renew the ancient Halych temples – fully buried the hopes of Halycians on the renewal of the Assumption cathedral. From his tailings the Domition church, the temple of St. Vasyl , was later built not far away and the Halych Castle in the modern town.