The Red Keep is made of pale red stone and overlooks the mouth of the Blackwater Rush. The Red Keep has seven massive drum-towers crowned with iron ramparts. The castle is smaller than Winterfell and is patrolled by gold cloaks. Much of the Red Keep is connected underground.

Massive curtain walls surround the castle, with nests and crenelations for archers. Thick stone parapets, some four feet high, protect the outer edge of the wall ramparts, where the heads of traitors are traditionally placed on iron spikes between the crenels at the gatehouse. The walls have great bronze gates and portcullises, with narrow postern doors nearby. The castle also has great cornerforts. The immense barbican has a cobbled square in front of it. Behind the walls are small inner yards, vaulted halls, covered bridges, barracks of the City Watch of King's Landing, dungeons, granaries, kennels, and stables.

The Red Keep has serpentine steps which can be strenuous to climb. Maegor's Holdfast, the small council chambers, the Tower of the Hand, the lower bailey, a small sunken courtyard, and the black cells are located below the steps. The Great Hall with the throne room is found above the steps, and the outer yard or ward is found near the main gate. Also above the steps are the godswood, the river walk, the small kitchen, and the pig yard. The royal sept and the Maidenvault are located above the serpentine steps as well.

Relics of the Targaryen dynasty, such as dusty suits of black armor, sit in some corridors. Doors are made of oak banded with black iron. Sweet-smelling rushes can be spread on floors. The Red Keep is full of cats, including those kept as pets as well as strays, like a black tomcat.