Gacka is one of the oldest Croatian provinces. Its inhabitants, the people of Gacka, have been mentioned as early as in the 9th century, for the first time in 818, during the time of the origin and formation of the early medieval Croatian state. Borna was the first Croatian ruler to be referred to as dux Guduscanorum, or the leader of the people of Gacka, so it was written in the Frankish Annals, while the people of Gacka were being reffered to as natio Guduscanorum

In the mid-10th century, the Byzantine Emperor, writer and philosopher Constantine VII Porphyrogenitus mentions the Croatian counties. Three of them, among the others were Gacka, Lika and Krbava - ruled by a Ban, while others were ruled by a Duke. In the early 10th century the province of Gacka belonged to the first historically known, Banovina of Croatia.

Throughout his history, the man had left behind a legacy of cultural goods in a modest extent. During long-term periods of security and peace, the culture in the area of today's Gacka was splendid and equal, or even superior, to other neighboring cultures. Thus, the Iapydes had lively contacts with the Etruscans, the most famous people of culture from the Appenine Peninsula, alongside the Greeks in the Mediterranean, and the cultural people of the Black Sea. The Iapydes stood as equal to those cultures, who are widely revered to be the most advanced peoples of the Ancient Era. In the times of tumultuous and fierce history, the muses were silent, and the remains of the material culture became a rarity. But still, all what man had created throughout the centuries was of outstanding cultural and immense artistic value, and it all happened here, in the Valley of Gacka.

Therefore, this area calls upon and reaches for the human imagination to reveal something uniquely magical and true in it's hidden beauty. This is Gacka, the Land and the Water.

In a historical and cultural sense, the region of Gacka is most famous for the Iyapodic culture. It was a grand, impressive, rich culture which lasted over a thousand years in continuity, from the 11th century BC. It is assumed that it continued coexist under the Roman rule, in parallel with the culture of the Roman conquerors, all the way up until a century or so AD.

The Iyapodic culture, which is increasingly being divided from the Illyrian culture by modern science, which considers the Iyapodes to be a separate entity and ethnicity, belonging to prehistory while indicating that something must have existed earlier as well, something out of which such a large culture could have originated from. The earlier period, which is also prehistoric because there are no written clues, preceded the Bronze Age and was part of the Neolithic period of the Stone Age. Between the earlier and later Stone Age, there was a transitional period, the so-called Mesolithic.

In the area of the Gacka region today, the Mesolithic spanned the period from around 10.000 BC to 6.500 BC. It was a time when man was still a hunter gatherer, the best proof of which is the Pećina located in the territory of the Gacka region.

Pećina is not a general name for every cavernous area, but rather is the name of the Pećina site near the spring Pećina in Lešće, close to the source of Kostelka, the tributary of the river Gacka from which that part of Lešće get's it's name from.

The Lešće Pećina is truly impressive, the aperture is large and its floor gently slopes into the depths. Certain archaeological excavations have documented traces of carbonised wild animal bones (hunter) from the Mesolithic period. The bones have visible traces of damage made by the usage of stone tools, tho the traces of this culture have also been found in the later, Iyapodic period. That is Pećina’s testimony of its use during a very large time period, some of it in continuity, some interrupted.

This archaeological site is basically in the palm of the visitors’ hands. One only needs to gently ascend some hundred meters from the spring Pećina, i.e., the Croatian Centre for Indigenous Species of Fish and Crayfish in Karstic Waters and descend to the other side to the cave, use his/her imagination and try and return a few thousand years in the past for the full immersive unique experience of History itself. The rock shelter comes with the forest and water, the springs - the entire prehistoric comfort.

Enjoy the pristine nature, the return into the past and discover Pećina in Ličko Lešće, an impressive first-class tourist site!

The Gacka region is the second Croatian destination according to the number of Mithras’ shrines, right after Salona near Split. Besides this shrine, a second one can be found in Rajanov grič in Čović, a third one on the slope of Godača in Sinac, while one relief plaque ended up in the Archaeological Museum in Zagreb, at one time having been found in the stone fence of the vicarage in Sinac. Apart from the above-mentioned, several more stone inscriptions have been found mentioning the pagan god Mithras because, according to the belief, Mithras was born from stone. The Gacka region is the second Croatian destination according to the number of Mithras’ shrines, right after Salona near Split. Besides this shrine, a second one can be found in Rajanov grič in Čović, a third one on the slope of Godača in Sinac, while one relief plaque ended up in the Archaeological Museum in Zagreb, at one time having been found in the stone fence of the vicarage in Sinac. Apart from the above-mentioned, several more stone inscriptions have been found mentioning the pagan god Mithras because, according to the belief, Mithras was born from stone. In the Late antiquity, Mithraism was also popular in the Gacka region, brought by Roman slaves, traders, and craftsmen. 
The Mithras shrine in Kraljev stolac was carved into stone, while the relief depicts the most important event of the Mithras cult - tauroctony, i.e., the moment when Mithras slays a bull. Mithras is depicted as a young man in a Phrygian garment, kneeling on the bull and holding it by its nostrils.
Rituals were performed in front of the Mithras’ shrine, but not much is known about them today because they were a tightly guarded secret. This religion was reserved for men only, while the cult members were connected as brothers.
The cult followers each had went through seven degrees of initiation and ate bread with wine to commemorate the Mithras and Sol Invictus banquet after sacrificing the bull.