Outstanding Special Effects!!!
I just watched this film on TCM (for the first time in many years).
You can say what you want about its historical accuracy, but the SFX are in fact excellent by 1970's standards, when they only had the use of models & glass plates & trick photography, with no CGI.
The inter-cutting of actual film footage from 1937 was also very well done.
This alone makes it worth watching.
M