Boom!
Boom is a great 1968 film, yes a "failed art film" with Liz and Dick. A campy version of the Tennessee Williams play "The Milk Train doesn't Stop Here Anymore",which I saw Off Off Broadway in the '80s. But most of all for me it's an integral part of the continuum of the infinitely mystical '60s era. FYI filmed on Sardinia (not Greece) August 1967 - 22 October 1967.
https://www.youtube.com/watch?v=zzACtH3_Kr8
https://www.youtube.com/watch?v=hc6z4q8QBL0