"Zum Goldstein" was first documented in 1568 and registered as an operating brewery in 1747.
Mainz had over 20 breweries at the time - "Zum Goldstein" being the 2nd largest - for the simple reason that well water was more than dodgy and the risk of contracting the Dreaded Lurgi from beer and wine was significantly lower.
Folk still say "Was soll ich Wasser trinke un kronk wern, ich trink liewer Bier odder Woi un bleib gesund!" - Why on earth would I want to drink water and get sick, I'll stick to beer or wine and stay healthy.."
A wise strategy and one that I can thoroughly recommend...
"Zum Goldstein" was swallowed by the larger Mainzer Actienbrauerei in 1860, closed down and reduced to selling their product until 1878 when a fire and significant roadworks emasculated the original structure.
These days, it's one of the best places in Mainz to chill out, eat well and enjoy the (Bavarian) beer.
Just stay off the water - you never know where it's been...