The name of the church of San Giovanni in Foro derives from its location: in fact, it stands where once stood the decumanus maximus and bordered directly the ancient Roman forum of Verona. There is no certain information about its origin, but it seems to date back to the 8th century.

The legend concerning the Church of San Giovanni in Foro has as its main subject the public barometer on its façade. Under the sarcophagus there is a slab to which everyone recognises a special virtue: predicting the weather. Technically, it is called a 'hygrometric stone', i.e. a stone capable of measuring the humidity in the air.

According to the legend, this slab predicts the weather in a very simple way: if you touch it and it is dry, the weather will be good; if you touch it and it is wet, it will rain.