Multiple Languages

I have a requirement to allow end-users to switch between English and Spanish on a given web site. I’ve looked over a bunch of plugins, but it seems that most are deprecated.

Basically, what I’m looking for is a way to add content in both, English and Spanish to the same Page or Post. On the front-end, one or the other would show up based on the user’s selection.

Any suggestions?

Thank you,
Alex