Sualkuchi, a town in Assam, is famous for being a silk centre. Option 1, a bird sanctuary, is not correct as Sualkuchi is not known for any bird sanctuaries. Option 2, a temple city, is also not correct as Sualkuchi is not known for having a large number of temples or being a religious center. Option 4, a hill station, is also not correct as Sualkuchi is not located in a hilly area or known for its scenic hills.

However, option 3, a silk centre, is the correct answer. Sualkuchi is renowned for its silk production and is often referred to as the "Manchester of the East." The town is known for its traditional handloom silk weaving industry, and the silk produced here is famous for its quality and intricate designs. Sualkuchi silk, especially Muga silk and Pat silk, is highly prized and is used to create beautiful garments like sarees, shawls, and traditional Assamese attire. The town attracts tourists and buyers who visit to witness the silk production process and purchase exquisite silk products.