I've never really understood why simply mentioning Sivasagar caused hilarity among my fellow anglo-saxon travellers. There isn't much to do in this town, aside from the three rather original Ahom temple-towers: Devidol, Vishnudol and Shivadol.
Some tourists choose to spend a night to visit these monuments as well as to make a stop on the route to Nagaland, or returning from there. For me, Sivasagar is limited to two lunch stops opposite the bus station (pratical).
If you go to Nagaland on the road, don't miss any of the tea picked by women dressed in coloured saris. Then very quickly, you leave the Hindu Assam to drive into the crests of Nagaland. From the border, I found that the landscapes, the architecture of houses and the faces of indigenous people changed a lot compared with the rest of my trip to India.