Where is my menu editor

So I've opened up a WordPress site I've developed some time ago where I've never had to use the menu editor. Problem is, I do need it now, but it doesn't show up in the wp-admin 'Appearance' section. I've checked my functions.php but there's nothing in there that instructs to hide it. I've searched Google for an answer but menu-plugins are kind of in the way for good doc results.

Is it hidden by default nowadays? How can I make it to show up?