After 45 minutes of searching through the bewildering maze of Venice’s pedestrian byways, we finally found our goal. "Caccia al tesoro!" -- "A treasure hunt!" -- exclaimed Mariacristina Parravicini, the Italian-born New York dealer. Treasures indeed were to be found at the Palazzo Fortuny, a splendidly dilapidated, four-story gothic building just off the Grand Canal, midway between the Rialto and Accademia bridges.