a very large dry-moated enclosure. This photo only shows part of the front area, and the enclosure also extends back well beyond the trees (it may be possible to see part of the fence-line if you enlarge the photo).
The lions were signposted as Asiatic lions but they may be hybrids.
For everything else at the zoo, see my review here:
http://www.zoochat.com/254/visit-assam-state-zoo-guwahati-10-a-358287/