Akhaltsikhe's main attraction is the Rabati fortress complex, which takes a couple of hours to explore properly. The Samtskhe-Javakheti History Museum inside the fortress is worth including in that time. Beyond the fortress, the old town around it has some characterful streets and a functioning mosque — the only reminder of the town's long Ottoman era in everyday use.
The town's real value is as a base for the wider region. Vardzia, the extraordinary cave monastery cut into a volcanic cliff south of the town, is an essential day trip. The regional springs at Borjomi are about an hour north.