I manage to get lost almost every time I come here, but eventually find my way to this charming 5th- or 6th-century church, with its comfortable, shaded courtyard. Indeed, what a tempting fantasy to think of taking over the caretaker's job, sitting with a book in the little shelter in the courtyard, tending the flowers, and unlocking the church for visitors -- who are bound to be impressed, because nothing about Osios David's simple exterior can prepare you for the glorious mosaic of the vision of Ezekiel inside. The vision shows Christ surrounded by the symbols of the four apostles (the angel, eagle, lion, and bull). If there's a more moving mosaic in Thessaloniki, I've yet to see it! According to local lore, this mosaic spent several centuries hidden beneath a calf's skin, which prevented the Turks from finding and destroying it. Osios David was built over (and used building blocks from) the remains of a once flourishing Roman bath, yet another example of the architectural recycling so popular throughout Greece. According to legend, the first chapel here honored the emperor Galerius's daughter Theodora, who converted to Christianity, and hid a tiny Christian shrine in the tumbledown bath complex. When Galerius learned of her deceit, he first imprisoned her in her own chapel and later had her put to death when she would not renounce her new faith. If you wish to see the mosaics more clearly, ask the caretaker to turn on the lights -- and slip her something for her troubles.