We then took the boat to Varenna ...
... and visited two other gardens there: Villa Muonastero, which is more like a botanical garden
and Villa Cippresi, which is actually a hotel (there was a wedding going on, but we sneaked in anyway)

Finally, we took the boat to the opposite shore and visited Mennagio and the fabulous Villa Carlota at nearby Cenobbio. This one was another favorite, it's just amazing.
More photos at Flickr:
Villa Cippresi
Villa Muonastero
Villa Carlota
Varenna