When in AD 9 they broke the resistance of the militant Illyrians, Delmatae and Pannonians, the Romans began to build roads, bridges and forts. One of the small military camps, which could accommodate a cohort of four hundred soldiers and a hundred horsemen, was situated in the area of Ljubuški. Most researchers assume that the camp was located at the site of Gračine in Humac, four kilometers southwest of the center of today's Ljubuški. According to numismatic, metal and ceramic finds it was built in the AD 1st century, probably during the reign of Tiberius (about AD 14), when the road Salona – Narona was completed. Its role was primarily strategic and defensive – to protect the valley of the River Neretva and the area of the colony Narona from the intrusion of the Illyrian peoples from the hinterland. Prehistoric communication from the interior towards mouth of the River Neretva, with Narona, a rich market town and a dream of many attackers, led through the Trebižat valley. Already in 1867 Brother Petar Bakula wrote about the remains of tiles and carved stones in the area of Humac, near the later Franciscan monastery, at the site Gračine. Archaeological excavations were carried out from 1977 to 1980, when only one part of the Roman complex was examined in an area of 2350 square meters, which is perhaps a fifth of the total complex. Material for the construction of the walls comes from the nearby quarries in Bijača, Hardomilij and Crveni Grm. Today only a small Roman quarry in the area of Bijača is still visible, while quarrying of the stone for construction is done in Crveni Grm. It is a local limestone (CaCO3). The walls were made of regular stone blocks of varying sizes. They were connected using mortar and lime. The central part the complex, whose walls are preserved to the height of a meter and a half, was made of nine interconnected rooms. Those were the baths with hot and cold water. However, it was mainly used by the military and civilian elite. Near the camp there were a lot of accompanying craftsmen - blacksmiths, hairdressers, shoemakers, stonemasons, gunsmiths, and probably a military brothel. In the first four rooms there were pools of hot water (caldarium) under whose floors, made of plaster, brick and covered by blocks, hot air circulated and warmed them. Next to them there were saunas (sudatorium) and pools of cold water (frigidarium). Remains of the furnace room (praefurnium), where the service would light a fire and heat the system, are preserved east of the baths. Next to the pools there was a changing room (apodyterium), a walkway (ambulatorium), a semi-circular space for business meetings and one latrine (a toilet). Waste water flowed down the stone channels to Trebižat.
South of the baths remains of a simple building were excavated, with hallways and small rooms. Those could have been warehouses and dwellings for the servants and artisans. The question remains how the Romans brought the water to the swimming pools in Gračine, if it is known that the River Trebižat flows ten meters below the complex. Some researchers believe that the water came by channel from the spring in Vitina, which is still nowadays a source of water for Ljubuški. However, a more realistic assumption is that the water was drawn by special devices to a higher level from Trebižat (turrim ad aquam tollendam). Roman writer Marcus Vitruvius mentioned somewhere in altitudinem aquam educere (to bring the water to a height), which means that Roman engineers dealt with the matter. For example, a copy of a bronze water pump from the 3rd century is kept in the British Museum. In the complex itself a lot of fragments of roof tiles and bricks were found, several metal finds of various tools and weapons, glass finds, ceramics and copper coins. Several fragments of tiles with stamps of military units were found, so it is assumed that the legions and cohorts made roof tiles and bricks for construction in furnaces. In the area of Ljubuški several tombstones of Roman veterans and soldiers were found. They belonged to different legions - most of them were members of VII Legion, then of IV Flavius' legion, XI Legion and VII Augustan Legion. When it comes to auxiliary units, most monuments were left by members of the I Belgian cohort, III Alpine and I Hispanic cohort.
After Gaius Marius' reforms in the 1st century BC the role of the military kept growing and became at the end of the Republic the most powerful state institution. Legion, divided into ten cohorts, still remained the basic organizational form. In territorial terms, army was divided according to the provinces, each led by the governor of the province. Legions were mostly made of Roman citizens volunteers (voluntarii), usually aged between 17 and 20. After on average 16 years of military service, sometimes even more, when retiring (missio numaria) soldiers received a severance pay equal to 13 annual salaries, and a diploma made of two attached bronze leaves. If there was no money for severance pay in the cash register, they could get the land instead (missio agraria). Roman army stood out with its excellent construction capabilities. During peace times, Roman army corps engineers built not only camps and forts, but also many roads, bridges, water supply systems, public buildings, and cleared forests and reclaimed marshes. There is a doubt whether what was excavated at Gračine is a Roman military camp, which had a strict layout and use of the premises, or an ancillary part of a military complex with baths and craftsmen's workshops and dwellings. Unfortunately, research results have not been published about Gračine, nor has further research continued. Time has taken its toll, so remains of the Roman complex are nowadays in quite a run-down condition, with unresolved property rights and illegal construction, although the site is included in the list of monuments of national interest. The value of the property at Gračine lies in the fact that this is the only partially explored Roman military complex in Bosnia and Herzegovina.