How do I display a 404 error page and serve a 404 status code without changing the url in a MVC 5 application

See more:

C#

redirection

MVC5

url-rewriting

Like the title says, I want to be able to display an error page and send a 404 header while keeping the url of the page that could not be found. What would be a good approach for achieving this?

What I have tried:

I've looked at attribute routing bu can't seem to wrap my head around how I would use it to achieve what I'm trying to do.