On a low hill west of the cathedral lie the partial remains of Chieti's Roman amphitheatre — built in the first century AD, large enough for ten thousand spectators, and now framed by an attractive park. The site was excavated in the late twentieth century and is now part of an open-air archaeological park known as La Civitella.
Set above the amphitheatre is the Museo Archeologico La Civitella, a smaller and more focused museum than the National Museum in the Villa Frigerj. It tells the story of the ancient city itself — Theate — through inscriptions, mosaics and household finds, and pairs nicely with the bigger collection downhill.