The relics supposedly released a holy oil that had healing powers. The principal shrine of the monastery is his tomb between the two adjacent churches of the old complex. The older church of Theotokos is the only known one on mainland Greece to have been built in the 10th century and the oldest example of the cross-in-square architecture, similar to the style in Constantinople. The adjacent larger cathedral-like church is set to date from 1011, featuring the earliest existing domed octagon construction with 8 piers going around its perimeter.
The interiors were supposed to be the most lavish in ancient times, and although there is a lot to see in terms of decoration and embellishment, not much has remained of the original. Still, Osios Loukas is a sight to behold, exuding mystic energy in a naturally serene environment. Today, this religious complex is considered one of the most notable among monuments of Middle Byzantine architecture, and is listed as a UNESCO World Heritage Site in Greece, alongside the monasteries of Daphnion and Nea Moni.
There’s a shop for local products, icons, etc. that you can visit and buy from as well.