Clustering of Forts
There are clearly three different clusters of forts in this map. The top half of the map contains two clusters, one to the west of the hill range and the other to the east. A thin ridge connects the two clusters and a bulge of plains that also extends southwards with Gadag at the center of this plain region.
The third southern cluster is obviously meant to protect access to the Tungabhadra river south of the cluster.
Thanks to Siddeshwar for pointing out some of the forts listed in this post and for putting up pictures from his travels to those forts at his blog.
While looking for more information on the fort at Gajendragarh, I chanced upon a blog post that referred to two more forts around Gajendragarh.
One has to take the Gudlur route from Aihole, which is approx 30 kms and further onwards it is 22 kms one comes into Gajendragarh one of the massive forts. There two more fortifications enroute to this fort along with a Kalkakaleswar temple.
The area turned out have six more fortifications. Looking at the size and shape of the fortifications, I am inclined towards these being sarais or caravan stations than forts.
The fortifications between Aihole and Gajendragarh
The northernmost fortification overlooks Aihole. The remaining five are concentrated around Gudur.