This need was served by the Katagogion, a term the ancient Greeks used for buildings that provided accommodation for many people – a kind of guesthouse.
Constructed in the early third century BC, the Katagogion was two-storeyed and had 160 rooms. It is quite a distance from the sanctuary proper and was perhaps built outside the sacred precinct wall (peribolos), as its role was utilitarian and not cultic. It was a large square building, of side 76.30 m., divided into four squares of equal size. In each square section there was an internal peristyle court with Doric columns, a separate entrance and access to one of the other courts. All four courts were surrounded by rooms of different sizes.
There was internal communication only between the two north sections and between the two south ones, possibly for medical reasons. That is, there may have been different wings for the patients and for the persons accompanying them, who came from all over Greece.
The Katagogion was repaired and underwent alterations in Roman times. Architectural members from the destroyed superstructure were reused (spolia) in the construction of the perimetric portico, with which the sanctuary – which was continually shrinking – was reorganized in Late Antiquity. Visible today are the stylobates of the internal colonnades, several thresholds of entrances, and remains of the Roman reconstruction.