its a heritage of the hindus and Pakistan,better stay in original context, who gives us the authority to say if its useless or not? do you have emotional or religious feeling attached to it? No, but the Hindus have. and we must respect that.
In Europe, Churches which become useless, are sold, and are bought by Muslims to be converted to Mosques...
I do not see, why these buildings should be an exception to that. There aren't any idol worshippers, so those are just useless buildings.