Ratna Sagar is located south of Nepal Eye Hospital, Ramananda chowk of Janakpurdhm Sub-metropolitan city. The Radha Krishna temple is north, Hanuman temple is east, Ratnasagar mandir is south, and North West of mata chhatrabas. King Janak kept his own property like silver, gold, and utensils in the Ratan Sagar lake. This sagar is famous by the name of the lake. Shri Ram Janaki’s statues are kept in this temple with Laxman, Radhakrishna, and Hanuman. It was founded by Shri Raghunath Das, was a saint who came from the banks of Ganga. This temple is built in the Gumbakar Shikhar Style. Religious festivals such as Vivah Panchami, Ramanava-mi, Janaki Navami, Jhula, Phagu Purnima, Anna Kutta, and Kojagrat Purnima are celebrated in this temple.