Sargent's interest in the beautiful pavement of Italy is really quite fascinating. Although this particular watercolor is not dated (by the source I had) he was in Sicily to see the Cathedral in Palermo (according to Olson) in 1897. The following year (1898) when he went to Venice, he painted the remarkable work titled "The Pavement" at the Basilica San Marco. 

All of this really begs the question of the most peculiar recent sale of an oil I call: "Venetian Interior Pavement". Could this be one of these paintings of this period when John was so interested in the mosaic floors? And what got him so fascinated with this subject matter? 
 

Note: 

Sold Christie's; 3/14/91; Lot 70; $20,900