Bongaigaon is a busy Lower Assam town and rail junction. It is not one of Assam's graceful old river towns, but it has enough nearby nature and archaeological stops to reward a spare day if you are already in the western Brahmaputra valley.
The town itself centres on Bagheswari Hill and Bageshwari Temple. The better excursions are just outside it: Kakoijana's forest, Koya Kujiya's wetland and islands, and the rock-cut caves around Jogighopa near the Brahmaputra.
Use Bongaigaon as a practical base rather than a romantic one. It has trains, buses, food, and onward transport, and the worthwhile sights are scattered enough that a car or hired taxi makes the day much easier.