Санкт-Маргаретен
He was the founder of the International Sculpture Symposium. He held his first international symposium ("Symposion Europaischer Bildhauer") with 8 participants in the old quarry "Römersteinbruch" in Sankt Margarethen im Burgenland. Prantl was invited to exhibit work in the Austrian Pavilion of the Venice Biennale in 1986.