The Greek word stylos means “column” or “pillar,” and a Stylite was a saint who lived atop a pillar as a form of asceticism, in the same way that an anchorite might be permanently immured in a cell or a hermit dwell in the woods far from civilization. Stylites were a feature of the Late Antique east, and were widely admired, although not widely emulated – such a life was not for everyone! Food would be passed up to them, and they might poop over the edge, producing relics for the faithful to take away.
From John Sanidopoulos, a blog post about the last remaining Stylite tower (hat tip: Tim Furnish):
While there is much written evidence about the Stylites, there is little that is left physically these days. But one of the only Stylite Towers that remains in the world is in Jordan, at a site called Um er-Rasas. In fact there are two, but only the base remains of the second tower. The ancient Jordanian town of Um er-Rasas is home to 16 historic churches, some with well-preserved mosaic floors. The most astonishing remnant of Um er-Rasas might be the Stylite Tower, one mile north of the city walls. Narrow, square, and tall, the tower offered a literal isolation from the world – a separate place where monks and ascetics endured mortification of the flesh wile entirely dedicated to fasting, prayer, and contemplation – sometimes for years on end. These towers were widespread in the early medieval pored; the 43 foot-high tower of Um er-Rasas, which can only be climbed by ladder, is the last of its kind in the Middle East. Ornamented with carved Christian symbols on all four sides, the square pillar endures in the distance as evidence of the once flourishing community established in the Roman/Byzantine era as a center for spiritual enlightenment.
More photos at the link. I should point out that Wikipedia claims that the tower “has been interpreted” as a Stylite tower, which suggests that there might be some question about its true function.
Here is an image of Daniel the Stylite (409-493), who lived for thirty-three years atop his pillar to the north of Constantinople.