This white marbled architecture is a memorial site of a Rajput clan. This cenotaph was built in the 19th century by Maharaja Sardar Singh in the memory of his father, Maharaja Jaswant Singh II, the 33rd Rathore ruler of Jodhpur.
One should visit this memorial, which has a temple like architecture, on their tour to Jodhpur. Jaswant Thada is a perfect example of architectural brilliance. The architecture is made of white marbles which are so fine that the outer surface of the whole building emits a warm glow during sunlight. Currently it exhibits a variety of paintings and portraits of Jodhpur rulers.
https://www.tourmyindia.com/states/rajasthan/jaswant-thada-jodhpur.html