Gonio Fortress — known to the Romans as Apsarus — is one of the best-preserved Roman fortifications in the southern Caucasus, standing at the mouth of the Chorokhi river about 12 kilometres north of Kvariati and 15 kilometres south of Batumi. The rectangular walls, reinforced with round towers at the corners and along their length, date from the 1st–2nd centuries AD and survive to considerable height. It is an impressive sight: a proper Roman castra plonked on the Georgian coast, looking across to the green hills of what is now Turkey.
The fortress protected the mouth of the river and controlled the trade route between the Roman Black Sea ports and the interior. Coins, pottery, and fragments of mosaic have been found here; a small museum inside the complex displays some of the finds. The site is easily reached by marshrutka from Batumi or Kvariati — ask to be dropped at Gonio — and makes a natural half-day excursion. The surrounding village is pleasant for a wander, and there's a simple café near the entrance.