San Geminiano

Plaque to Sansovino's church of San Geminiano, Venice
When I look at the two plaques which mark the spots where churches dedicated to San Geminiano once stood, I am tempted to paraphrase Lady Bracknell's observation in The Importance of Being Earnest...

To lose one church may be regarded as a misfortune; to lose two looks like carelessness. (Venice has, in fact, lost three churches dedicated to the fourth century bishop-saint). 
Plaque to the first church of San Geminiano, Piazza San Marco, Venice
San Geminiano first stood on the west side of the Rio Batario, the canal which once ran through the piazza. The church had been built in the 6th century and was demolished in the 12th century when the piazza was enlarged. A small plaque marks where it stood. Sadly, we have no idea what it looked like.
A detail of the Barbari map, 1500, showing the church of San Geminiano in the Piazza San Marco, Venice.
San Geminiano was duly rebuilt at the western end of the enlarged piazza and we do know what this church looked like, as we can see it in the Barbari map of 1500. Five years after the map was printed, work began on rebuilding the church for a third time. 

The architect was Cristoforo del Lagame (no mention of him in the plaque). However, funding dried up before the church was complete. In 1557 Jacopo Sansovino finally added the façade, which can be seen in an engraving by Luca Carlevarijs, and the central dome. 
The church of San Geminiano in an engraving by Luca Carlevarijs
Two hundred and fifty years later San Geminiano was demolished to make way for the building of the grand staircase and ballroom of the Palazzo Reale, which was located in the Procuratie Vecchie. The church was never rebuilt. 
Sotoportego S. Geminian, Venice
In addition to the plaques, the memory of San Geminiano lives on in the name of the sotoportego, which stands on the site of the third church.