On the way between Trebinje and Mostar (around 5km from Trebinje) lays an old monastery surrounded by wineyards. The monastery was built on the foundation of an old church, and the 4th-century foundations of the first Roman church on the site are still visible today (inside the curch, below the glassbottom). This shows also how long there is christian religion in Hercegovina.
In the first half of the 6th century the monastery was the biggest scriptorium of the Slavic south, and at the same time cultural and spiritual center of a broader area. The Orthodox monastery was established there in the 15th century, with a cathedral constructed about 1508 and painted with murals by Vicko Lavrov from Dubrovnik (1517) and from monk Marko Stefanov Trebinjac (on the same period).
This was also the period when Viasilije Ostroski (the holy monk from Ostrog Moanstery in Montenegro) arrived to Tvrdos to become a monk. His modesty forbidding him to push himself forward to occupy the high positions his piety and capabilities recommended him for, he was elected as Bishop of Zahumlje and Skenderia against his will.
He had the capacity to help the orthodox population of the area not to succomb to islamisation by the turks or to catholization by catholic missionars.
The monastery remained a seat of the Metropolitans of Herzegovina until the Ottoman Turks destroyed it in 1694 (in the fights between Venetians and Turks). That was also when Vasilije Ostroski fled to Montenegro.
Actually Tvrdos had been frequently destroyed and reconstructed before. The current building of the monastery was constructed in 1924. Today the monastery is temporarily the seat of the Eparchy of Zahumlje and Herzegovina (otherways the seat is in Mostar).
Tvrdos was built to give protection from attacks, a massive wall is built around the monastery.
The monastery is also known for the good wine the monks are making and also for the honey. Because of that it's on the wineroute of Hercegovina (here the site) and here is the website of the monastery (in serbian).