Does Spanish have an equivalent of the pronoun "one"?

Question

In English, one can use the gender-neutral indefinite pronoun "one", e.g.:

One does not simply walk into Mordor...

In most dialects of modern English, this is rarely used, being replaced by the impersonal "you".

Does a Spanish equivalent of the pronoun "one" exist? As in German man/einer, French on, Catalan hom etc. Or is the only option to use the impersonal se?

Answer 1

Though it is indeed more common to use the impersonal se in analogues of such phrases:

No se entra así como así en Mordor...

Spanish does have such a (subject) pronoun:

uno², na
...
11. pron. indef. m. sing. Designa a una persona indeterminada.

Uno debería saber cómo comportarse en esos casos.