The Sphere Tank has 3 significant features. Three oil silos, the massive sphere with catwalks and then the two small shacks on the ground. The silos have stairs going around them to climb to the top of it, where you should find a lot of Loot Crates and mostly Barrels which contain loot or oil. The staircase and the top of the silos are kind of guarded by sheet metal and sandbag barricades. Underneath the metal sphere you can find many more barrels. The main part of this monument is inside of the Sphere Tank itself, where you can find a lot of loot aswell, but with the risk of parkour. Play safe!