LISP is one of those languages. Very old, but still very relevant. And probably the most beautiful language ever. Some languages you learn because you want to use a framework, other times you learn them to run code on a certain device or even because of the job market. But you also have languages that you should learn because they will bring a different perspective to stuff. Both Haskell and LISP is like that.
LISP is not one language though. You have many different versions. The most popular ones are probably Common Lisp, Emacs Lisp and Clojure. My advice is to start with Clojure because the tools are much better and it is just much easier to work with than some of the other Lisp versions.
I have written about Lisp a few times because I think it’s awesome. It is a little bit weird, and it takes a while to get into it. But you kind of don’t care that much for other languages once you get into it.