dependent clause without independent clause

To boldly go where no man has gone before.

I cannot understand the meaning of this sentence. Would anybody like to explain the type of structure of this sentence as well as the meaning of this sentence? I don't find any subject and main verb of it. Due to presence of where it seems to me that the rest of sentence after where is the part of dependent clause, i.e it indicates that where no man has gone before is dependent clause. So where is its independent clause?