propylaion

Propylaion refers to two notable uses of the term in architecture and in modern data science. In classical architecture, the singular propylaion (often rendered as Propylaea in English) denotes the monumental gateway to the Acropolis of Athens. Built in the mid-5th century BCE as part of Pericles’ building program, the Propylaia served as the ceremonial entrance to the sacred precinct and was designed to harmonize with the surrounding monuments. The complex consisted of a central gateway structure and flanking wings, establishing a dramatic ascent from the city up toward the Acropolis. Today, only portions survive and the site has undergone later restorations, but the Propylaion remains a key example of high Classical Greek architecture and the integration of functional gateway spaces within a sacred context. Its name derives from Greek words meaning “before the gates.”

In contemporary usage, Propylaion is also the name of an open, collaborative project that aims to provide large-scale, publicly available image–text data for training vision–language models. The project seeks to promote transparency and reproducibility by releasing datasets and accompanying code that enable researchers to study data collection, licensing, and model training without relying solely on proprietary datasets. Notable releases include large-scale versions such as Propylaion-1B and Propylaion-5B, consisting of billions of image–caption pairs drawn from publicly licensed or cleared sources. Propylaion emphasizes open data practices and invites community participation, while contributing to the broader discourse on copyright, provenance, and responsible use in AI research.