The regatta was an annual carnival event in Venice from the 14th century onwards, and continues to this day. While regattas were sometimes held in honour of distinguished visitors, the regatta in the painting appears to be the annual carnival event. The pavilion at the left is a temporary structure from which the prizes were presented. It bears the arms of the Doge Alvise Pisani, who ruled from 1735 to 1741.
The National Gallery, Trafalgar Square, London WC2N 5DN