In the little courtyard or “atrium”, inside the portico but outside the main doors of Old St Peter’s (and you can follow the tag below for many images of the church), stood a little fountain.
It included a colossal pine-cone of bronze, which will be familiar to many who have visited the Vatican[ref]Photo from Wikimedia Commons, by Wknight94, April 2008.[/ref]:
I found online at Google Books[ref]A. van den Hoek & John H. Herrmann Jr, “Paulinus of Nola, courtyards and canthari: a second look”, In: A. van den Hoek &c, Pottery, Pavements, and Paradise: Iconographic and Textual Studies on Late Antiquity, Brill (2013), p.45, fig. 13.[/ref] the following copy of a drawing of the fountain, itself taken from Huelsen[ref]C. Huelsen, “Der Cantharus von Alt-St. -Peter und die antiken Pignen-
The Huelsen article includes further drawings.
Another image comes from a manuscript, Ms. Brussels 17872, fol. 56v, by Philipp de Winghe, and made around 1591-2.
Supposedly water would come out of the pinecone at various places, although how I don’t quite know. The pinecone and two of the peacocks have survived, as may be seen above.