 Complete the following phrase:  Silsako was an ancient stone bridge over a channel of river Barnadi in Hajo, Kamrup. As the channel changed its course over time, now the bridge is stranded in the middle of a small lake. It was an important transit route in ancient and medieval times. Many invaders like Muhammed Bin Bukhtiyar entered into Kamarupa in the year 1205-06 AD, and crossed the bridge Silsako. This historical bridge sustained damage in the 