What are(were) these towers used for? The other pic is a hint.

Cracked by: shenoyvarun86, krudebox , udupendra , Dibyo , tete80 , Logik , duriel , Rogi , Siddharth Jain and Hitesh T S.

shenoyvarun86, krudebox, udupendra, Dibyo, tete80, Logik, duriel, Rogi, Siddharth Jain and Hitesh T S