It’s the principle offering at the annual spring feast to celebrate the city’s patron saint, Saint Mark the Evangelist; tradition has it that the very first peas of the season are used to make the risotto.
To celebrate In the Age of Giorgione, Polpo are giving away free dishes of risi e bisi to exhibition visitors. All you need to do is keep your exhibition ticket after your visit and hand it in at any Polpo restaurant.
(N.B. Their closest restaurant to the RA is a short walk away on Beak Street, which incidentally has a remarkable Venetian artistic connection - it was once the residence of the great artist Canaletto.)