According to the flyer, which is handed out at the entrance to the park, the fortress was built in the seventeenth century by Ali Beq. It served as a military stronghold to control a road through the Arbel valley and a sacred Druze tomb on the other side of the valley.
The fortress is located more or less below the Carob Lookout. But as you will see, it is neccessary to walk quite a round to get there.
Coming to Arbel National Park you certainly should do some hiking. I did a round trip around the cliff, which was really nice and scenic. This trail had some places where it was neccessary to use iron bars mounted in the rocks to get down and up the cliff. But there are other options to get to the different places without the need to climb. There is parking down in the opening of the valley between Mount Arbel and Mount Nitay towards lake Kinneret. From there you can walk up to the fortress. Also the green trail seems to be OK, regarding its difficulty.
I am sure you will enjoy it here!
From the Carob Lookout you will have a great view over the lake Kinneret and beyond. You can see the Golan heights and of course the very beautiful Arbel National Park itself. The lookout is located on the edge of the cliff of Mount Arbel. The cliff is a result of tectonic movements.
You will find signs (made of stone) showing landmarks of the region.
If you want to do the round hike, this place is where you can return in case you forgot water.