Tom, I don't know Villa d'Este personally. The various reviews of it in golf magazines etc don't suggest that it is too tight between the trees and the (not always reliable) Peugeot Guide suggests that you have to be able to move the ball both ways in order to score well. Peter Gannon is a mystery to me, and a quick web search revealed nothing new. He also had a hand in Milano, Varese, Degli Ulivi, Alpino di Stresa, Firenze Ugolino, sometimes in conjunction with someone called Blandford. Cornich suggests, 'Based in Ireland in the 1920s, james [Peter] Gannon designed Villa d'Este in Italy (1924)* the original nine at Lenzerheide in Switzerland and the original nine at San Abdres de Llavaneras, Barcelona, Spain.' * (Golfer's handbook gives 1926).
I'd happily put in El Saler - it strikes me that Javier Arana remains one of the unsung heroes of European golf design despite the unpsurge in Spanish golf tourism. I, too, enjoyed Noordwijk but there was some criticism of it on a previous GCA post so I left it out (criticism of the par 3s as I recall, which may be fair, they're not up with the top links short holes).
I'm very interested to see Club zur Vahr at Bremen getting recommendation as it has been in the World Atlas of Golf since the very beginning, yet I can never update the entry as nothing seems to have taken place there in recent years and I have not been there myself. Is Limburger another unsung hero of European golf design?