Much like ketchup and sriracha today, a fermented, fish-based condiment called garum was ubiquitous in the Roman Empire. The stinky sauce’s popularity is readily documented in ancient texts, but archaeologists have yet to unearth extensive physical evidence of its production. A newly discovered factory located about 1.25 miles outside the southern Israeli city of Ashkelon is, in fact, one of the only garum production sites ever found in the Eastern Mediterranean.

As Amanda Borschel-Dan reports for the Times of Israel, archaeologists working at the site, which was excavated ahead of construction, discovered fish pools, giant vats, and jars and receptacles used to hold sauce. The team also found wine-making equipment dating to the Byzantine era.

Garum factories have previously been found in the Western Mediterranean and North Africa, particularly in Spain, but only one other suspected garum factory is located in Israel. The researchers think the factory at Ashkelon wasn’t a major facility, but rather used to produce sauce for locals.

“This is a rare find in our region and very few installations of this kind have been found in the Eastern Mediterranean,” Tali Erickson-Gini of the Israel Antiquities Authority tells Haaretz’s Ruth Schuster. “Ancient sources even refer to the production of Jewish garum. The discovery of this kind of installation in Ashkelon evinces that the Roman tastes that spread throughout the empire were not confined to dress but also included dietary habits.”

Given the sauce’s enduring popularity, archaeologists have been puzzled by the small number of garum factories found to date.

“What interests me is the fact that this product was very, very popular in the Roman and Byzantine period,” Erickson-Gini tells Borschel-Dan. “As popular as it was, you’d expect to find a lot of installations.”

One explanation for the relative scarcity of production facilities posits that factories were built outside of towns and cities. Ancient sources report that the garum-making process was so stinky, laws were actually passed to keep production away from urban areas.

According to María José Noain Maura of National Geographic, garum factories, or cetariae, produced two main products: salt fish and garum. The animals gutted, salted and preserved to make the first of these culinary delights provided the fresh fish guts needed to cook garum; fermented in large vats for months on end, mackerel, tuna, whitebait and anchovy innards were layered between salt and aromatic herbs until they “reached proper pungency.” Then, workers strained the smelly goop, producing the much-ballyhooed amber garum. Allec, the sticky paste left in the strainer, was also widely traded but considered inferior to garum.

While garum was all the rage in the Roman world, Schuster reports that the sauce traces its origins to the Greeks and Phoenicians, who traded the fermented fish mixture as early as 500 B.C.

Erickson-Gini says garum was more than a simple condiment. More widely used than modern counterparts like ketchup and sriracha, it was an ingredient in many cooked dishes, imparting a salty, savory element.

Garum was enjoyed as late as the medieval period and likely only disappeared from European and Mediterranean cooking because the Roman trade routes that brought the sauce to inland areas were disrupted. Interestingly, new research suggests the fall of garum may have had positive ramifications: Per a recent study, uncooked garum was likely responsible for spreading fish-related tapeworms across the Roman Empire.

Catering to those willing to risk tapeworms, several modern cooks have recreated garum recipes. As Phil Edwards reports for Vox, many taste testers say garum offers a subtle take on modern fish sauce, teasing out the flavor of umami-seasoned foods.

All it takes to make garum at home is fresh mackerel guts, salt, dried herbs, a clay container, and a sunny spot where the concoction can fester for two months without being knocked over by raccoons—or neighbors angered by the stink.