Age old structure

This is a structure of megalithic age.Some time back I visited it along with my friends.It is located  on almost 500 meter height hillock.historians opined that these belonged to the humans beings lived some 2500 years back.I guessed the humans then built these to hide from  rain or heat or beasts perhaps.And these were their great houses too.I had a surprise ....how nicely flatten the roof with rock element...rocks seemed very heavy...what instruments could have used to lift it in a good position...!

This location is about 70 k.m.away from our place,named suraveedu .There are almost 100 structures like  this.I am very much interested in issues like this ...but I missed one more interesting structure here...hope to go next time.