A tank (7) adapted for storing liquids in general and made of reinforced concrete is obtained by coupling inner and outer staves (1) and (3) in the form of rectangular laminae curved transversely with different radii of curvature and provided with appropriate inner and outer circumferential grooves (15) and (17) arranged on the inner surfaces of two substantially cylindrical heads (11), said plurality of staves (1) and (3) constituting with said two heads (11) an empty case double wall (5) or planking adapted for compacting thereinto the appropriately reinforced concrete (9). The heads (11) are provided with a plurality of through holes (13) adapted for insertion of the metal reinforcing and anchoring elements. Appropriate stabilizing wedges (21) and spacer elements (23) ensure the stability of the tank (7) and the correct dimensioning between the heads (11) as well as the containment of the anchoring concrete (9) and serve as a pavement. Appropriate hatches (25) are provided on the upper portion of the tank (7) which has the form of a horizontal cylindroid solid.