It is built on a cliff where two rivers join. From the 10th century. Inside you will only find cows and smell some of their products. No entrance, no other tourists. It's next to the road between Vardzia and Akhaltsikhe
The medieval cave city was built by Queen Tamara. It can be reached by car in one day from Borjomi, but the road is very bad for the last 12 kilometer. Entrance fee 5 dollar. It's incredible beautiful but a lot of climbing too. Take food and drinks with you. You cannot buy anything overthere, it can be very warm in summer.
Aside from the Church of the Assumption and the monks' cells, the rest of the Vardzia complex consists of empty rooms. It is fun to explore though, stairways and tunnels connecting rooms on different levels, some rooms enormous and bare, others tiny yet detailed. In a few places, the steps have worn down and the rock has begun to fall away, so it might be dangerous to be too vigorous in your climbing, but you can still spend a couple of hours here if you are determined to seek out every room. If you are waiting for the bus back to Akhaltsikhe, you might as well do this, as there is sod all else to do down below in the village!
Take along a Georgian phrasebook (available in Prospero's Bookshop on Rustavelis in Tbilisi)...this will enable you to chat to the monks, who probably don't get so many foreigners to talk to. Of course, you are never going to be able to debate the meaning of life with just a phrasebook, but with a bit of crafty language work and many a hand gesture, you can have a conversation of sorts. They are friendly folk, as long as you respect the fact that this is a monastery first and a tourist attraction second...don't earn the scorn that the Armenian group did by shouting and screeching...noises tend to echo in caves.
If a monk spots you, he may unlock the Church of the assumption for you. This is the only church still functioning...there were several more, but earthquakes, attacks and vandalism have seen to those. Look out for the frescoes on the walls, especially the one of Queen Tamar. There is a donation box inside, and it is worth putting a few coins and notes inside. A monk may also lead you through a pitch black cave to drink the water from "Tamar's Tears". Not for the chlaustrophobic, you might want to bring a torch, otherwise you'll have to "put your trust in God" or at least in the monk and his candle. The water, if you manage to reach it without knocking yourself out on the low roof, is cool and sweet.
After buying you ticket, head up the twisting path passed a few derelict caves...you can look inside these if you want, but they are unfortunately filled with cigarette ends. After about ten minutes or so, you'll reach a belltower and a gate...this is the entrance to the monastery.