The hadronic calorimeter of the ATLAS experiment at the LHC

I shall report on the final prototype of the hadronic calorimeter being built for the ATLAS experiment at LHC. This calorimeter is made of iron and scintillating tiles. Light collection is realized with WLS fibers. The projective geometry of the calorimeter is obtained by properly grouping fibers which are then readout with photomultipliers. The main characteristics of the three main components of the calorimeter, i.e. scintillating tiles, WLS fibers and photomultipliers will be described together with the performance of the calorimeter prototype (resolution and linearity) as measured in test beam both in "standalone" configuration and in combination with the ATLAS electromagnetic calorimeter.