Most of the 1368 pieces that come with this set go into building the Helm's Deep castle. This castle is a front only model and not a complete castle, but as Helm's Deep in the movie is built into a rock face this is expected.
The LEGO Helm's Deep has a gate section with ramp, an inner keep, a tower and a section of the Deeping Wall.
All these pieces are closely modeled in what we see in the movie and with the inclusion of pieces that have stone markings on them and accessories such as flags and torches they look really good.
The Deeping Wall
This section is really cool with a grill where the stream passes through and a giant Uruk mine placed in it. A nice mechanism can be operated which blows up the wall and allows the Uruk-Hai mini figures to charge in.
The Front Gate
This has everything you would expect; the ramp leading up to the gate, the doors, the opening trap doors above for throwing down rocks, a mini catapult and a fun little device that shoots Gimli into battle.
This tower contains a ladder to the top and the horn which Gimli blows in the movie to sound the charge.
The Inner Keep
The keep is where King Theoden relaxes and contains his throne and dinner chamber complete with cups and food. There is a folding ramp which can connect the keep to the gate.