In the middle of the 14th century the hermit Varlaam climbed the rock, built a few cells and a small chapel which he dedicated to the Three Hierarchs. He lived there in seclusion, dressed in tattered rags and lost in prayer till the end of his days.
The buildings remained deserted for many years after his death but early in the 16th century two brothers, the monks Nektarios and Theophanis, scions of a noble family of Apsarades from Ionannina who had already spent seven years on the column or rock of the Forerunner in the monastery of Great Meteoron, ascended the rock and single-handed began to rebuild the church of the Three Hierarchs that Varlaam erected.
The two brothers mention the ascent they made of the rock in their will:
„Having found the wide and lofty and tranquil rock, called Varlaam after the monk Varlaam who lived upon it long ago and from whom it received its name, to be of ample space and acceptable to us as a habitation though uninhabited for many years and utterly desolate as a building ground, we commenced in 1518 to renovate and build upon it in order to make it habitable.“
Soon the number of the monks increased and they started building a second church, the katholikon, which was bigger and had to domes. In 1542 after finishing the building of the church, they dedicated it to All Saints.
The rapid growth of coenobitic life and the spiritual heights it attained there led to the monastery’s enrichment by the two founders and by gifts from the faithful of estates, vineyards, olive groves and metochia. Even after the death of two monks- Theophanis died in 1544 and Naktarios in 1550 – the monastery continued to flourish, attracting yet more monks.