How to tell what types are defined in a Delphi DCU?

I have a set of compiled Delphi dcu files, without source. Is there a way to determine what types are defined inside that dcu?

You could have a look at DCU32INT, a Delphi DCU decompiler. It generates an .int file that is somehow readable but not compilable, but if you only want to determine the types defined, this could be enough.