Who among the following built the temples at Basistha Ashram?

Basistha temple, located in the south-east corner of Guwahati city, Assam, India, is a Shiva mandir. The history of the Basistha Ashram where the temple is located dates back to the Vedic age. According to legend the ashram was founded by the great saint Basistha (Vasishtha). The temple was built by king Rajeshwar Singh.