The pyramid was built about 18–12 BC as a tomb for Gaius Cestius, a magistrate and member of one of the four great religious corporations in Rome, the Septemviri Epulonum. It is of brick-faced concrete covered with slabs of white marble standing on a travertine foundation. The pyramid measures 100 Roman feet (29.6 m) square at the base and stands 125 Roman feet (37 m) high.
In the interior is the burial chamber, a simple barrel-vaulted rectangular cavity measuring 5.95 metres long, 4.10 m wide and 4.80 m high. When opened in 1660, the chamber was found to be decorated with frescoes, which were recorded by Pietro Santi Bartoli. Only scant traces of these frescoes survive, and no trace of any other contents. The tomb had been sealed when it was built, with no exterior entrance, but had been plundered at some time thereafter, probably during antiquity. Until the end of restoration works in 2015, it was not possible for visitors to access the interior, except by special permission typically only granted to scholars. Since the beginning of May 2015, the pyramid is open to the public every second and fourth Saturday each month. Visitors must arrange their visit in advance.
A dedicatory inscription is carved into the east and west flanks of the pyramid, so as to be visible from both sides. It reads:
Below the inscription on the east-facing side is a second inscription recording the circumstances of the tomb's construction. This reads:
Another inscription on the east face is of modern origins, having been carved on the orders of Pope Alexander VII in 1663. Reading INSTAVRATVM · AN · DOMINI · MDCLXIII, it commemorates excavation and restoration work carried out in and around the tomb between 1660–62.