If you think anchovy paste is intense, you haven’t met garum , ancient Rome’s go-to condiment. This fish sauce was the umami bomb of its day, a salty, savory liquid that Romans drizzled over just about everything: humble street snacks, wine, banquet dishes, even sweets. First developed during the Republic, it became a staple across the empire, revered at once for its flavor, supposed medicinal powers, and serious economic clout. Not unlike hot sauce today, garum was as much a business as it was a seasoning.

Despite the singular name, garum was a broad category of salt-cured, enzyme-liquified sauces. The most prized varieties were made by layering the guts (and sometimes whole bodies) of oily fish—typically mackerel, anchovy, or tuna—with salt in open-air vats. The mix marinated under the Mediterranean sun for weeks or months, during which natural enzymes and microbes broke the fish down into a golden, translucent elixir. The top layer was garum proper. The gritty sludge left behind, called allec, was a coarse paste more likely to show up in a plebeian’s pot than on an aristocrat’s plate.

Other versions circulated, too, including liquamen (a term that sometimes overlapped with, and eventually replaced, garum in later sources) and muria, the salty brine left over from preserving whole fish. These sauces weren’t identical, but each had their uses in Roman kitchens and trade networks.

Garum production, which extended to coastal cities across the empire, required skill, patience, and a strong stomach. Producers kept a careful eye on temperature and smell, stirring the mixture as it ripened in the heat. The best garum was said to smell pleasant (yes, really) and fetched premium prices at market. Carthago Nova (modern-day Cartagena in Spain), the coast around Neapolis (modern-day Naples), and especially the provinces of Baetica (southern Spain) and Lusitania (modern Portugal) were famous for their sauces. Amphorae from these regions, stamped or painted with their contents, origins, weight, official seals, and even brand names, have been found from Britain to Syria.

Ancient garum factories weren’t mom-and-pop operations. They were industrial-scale production sites, with rows of fermentation vats, attached workshops, and easy access to ports for export. Amphorae used for garum were even specially shaped to reduce leaks and preserve freshness on long journeys.

In the kitchen, garum did what soy sauce or Worcestershire does today: provide an instant boost of depth and umami. De re coquinaria includes garum in recipes ranging from pork ragouts to stuffed dormice (would try). It even turned up occasionally in sweets; who said dessert can’t have fishy flavor? Modern chefs have taken note: Arcangelo Dandini prepares dishes with his homemade garum at his restaurant near the Vatican. The name of his restaurant in London’s Bayswater district? Garum, of course.