On the way from Rijeka to Trieste, in the settlement of Pasjak, we find the remains of a mighty fortlet with 3 m wide walls. Due to a small number of archaeological finds, its role within the barrier system is not entirely clear, but the fortlet definitely existed around the year 270.
The fortlet, located a few metres above the present Rupa–Starod road near the Slovenian-Croatian border, was built on the former Roman road Tarsatica–Tergeste. 200 m of the wall with both entrances were archaeologically excavated and conserved, while the rest is nowadays visible as a 4–5 m wide embankment extending over an undulating plateau. The Gradina above Pasjak fortlet is of an irregular quadrilateral shape and perfectly adapts to the diverse terrain. At each of both entrances, there are two rectangular entrance towers, where a stone threshold is also visible on the floor.
The Gradina above Pasjak fortlet is mentioned as part of the claustra Alpium Iuliarum barrier system with some reservations. Although the archaeological site has all the characteristics of Alpine barriers, it has no linear barrier walls. The rare archaeological finds also allow us only an approximate dating of the fortlet in the Late Roman times. The only exceptions are the rare monetary finds from the year 270, discovered at the foundation of the fortlet , on the basis of which we cannot reliably claim as to whether the fortlet was destroyed in 270 or built only after that year.