"The nine-level Temple of the Inscriptions stands just south of the Palace. Set directly into the hill behind, it is highlighted and framed by the landscape. After discovering that the floor slabs of the chamber could be moved to reveal interior constructions, the Mexican archaeologist Alberto Ruz cleared the staircase and in 1952 found the extraordinary tomb at the base of the pyramid, set on an axis, north-south, with the stairs.
Within, a large corbeled chamber held the uterus-shaped sarcophagus of the great king Pacal, whose remains lay covered with jade and cinnabar. The sarcophagus lid shows the king at the moment of death, falling in rapture into the maws of the underworld. The sides of the sarcophagus display Pacal's ancestors, emerging from the ground, while nine stucco attendants flank the walls.
The construction was designed for eternity: even the cross-tiers were made of stone (the only examples known) and a small stone tube, or 'psychoduct,' as it is called, connects the tomb to the upper level and thence to fresh air. The Temple of the Inscriptions in unique among all Mesoamerican pyramids in having been built before the ruler's death, probably to his specifications."
Mary Ellen Miller, The Art of Mesoamerica form Olmec to Aztec, p. 128-9.