Louvain climber from America?
I saw at the Louvain botanical garden a climber growing 30 feet high, that was unknown to the curator and that stood there for more than 40 years. It has opposite more or less ovale leaves and flowers of about 3/4 inch in cross section.
A detail of the flowers you see in the link. Has anyone an idea what species, genus of even family it could be?
Here is a link that might be useful: