3 Answers
+ 18
Another language which enforces indentations is Occam. Not sure if more exists.
In other languages, proper indentations are also considered good practices and norms btw. :>
+ 6
COBOL also requires indentation
+ 4
There are others, but for the majority of popular current languages indentation is only for readability and codeblocks are usually defined by keywords, curly brackets, or other punctuation like semi-colons, parenthesis etc. In those languages the compiler/interpreter will ignore spacing, newlines, tabs etc.