Along the Krka and Čikola Canyon, as well as in the Town of Drniš, there are the remains of several majestic forts and fortifications. Although some were built earlier, all are considered part of the medieval defense system, built and owned by Croatian aristocratic families Nelipić, Šubić and others. From 1322 the family Nelipić controlled Drniš, Knin and Cetina area, holding and controlling numerous properties along the left bank of the waterfalls. The system of medieval fortifications Ključica, Kamičak, Bogočin, Nečven and Trošenj is considered to be one of the largest and most significant historical defense structures in Croatia. Available for visitors are the fortress Gradina above town of Drniš, and an exquisite view on the fort Ključica can be enjoyed from viewpoint Ključica in the village Ključ.


Drniš Fort – i.e. medieval fort Gradina is located in Drniš, at an altitude of 344m above Čikola Canyon. Built on a strategically important point, it offers a majestic view on entire Drniš, Promina Mountain, Petrovo Field and Čikola Canyon. It is assumed that Gradina was owned by a Croatian aristocratic family Nelipić. During Ottoman rule, Gradina was upgraded in a defense object. Arriving to these parts in the 17th century, the Venetians ordered its destruction. But, the fortress was soon rebuilt due to constant Ottoman threat which lasted till 1715. In the 19th century the fortress was abandoned and used as a source of building material for the growing Drniš parts. Visible remains of the south side are a part of the medieval fort, whilst the central tower and the north-east defense wall derive from Ottoman time. Gradina is registered as a cultural monument.


Ključica fort is the largest, best-preserved medieval fortress in Drniš area and is a protected cultural monument. It was built by Nelipić family in the 14th century. It is located on the right bank of the Čikola Canyon, near the village Ključ on Miljevački plateau. It was built to enable the control of the Venetian trade routes from Šibenik to hinterland and Bosnia. The Nelipić family charged the crossing over bridge on Čikola, whose historical name in that period was Poljščica. For this reason, Šibenik aristocrat families organized an attack on Ključica and burned the fort. After a series of conflicts, Nelipić family in 1343 consented to tear the fort down. However, this did not happen, but Nelipići built several other, smaller forts. With time the Nelipić family influence and power decreased, and in 1450 the Venetians offered them 1000 gold coins to destroy the fort, or 200 gold coins to give control over the fort to Venetians. With the arrival of Ottomans, these conflicts lost meaning, as Ottomans took over the fort and controlled it from 1546 to 1648, after which it was abandoned.


The remains of the fort Kamičak are located on the left bank of the Krka River, along the footpath leading from Visovac Lake to Roški Waterfall. Although it is heavily devastated, with few preserved remains, according to the descriptions from the 19th century it looked like an "eagle's nest". Nelipić aristocratic family, heirs of the Svačić family, derive from this fort. Locally, the fort is also known by the name of "Utješinovića grad", as in the 15th century Utješinović family ruled Kamičak. The fort was demolished in 1522 by the Ottomans.