How can I render an existing complete web page within rails?

I’ve looked for an answer to this but not found anything dealing with
complete html pages.

I have a collection of complete web pages (harvested and localized by
wget) my app classifies these and presents the user with a list and I
would like to display the page when the user clicks a list entry.

At the moment I generate a clickable link with a full file://URL for the
page, something of which I am deeply ashamed.

What I’d like to do is render the file with my own close button at the
top. The page itself should be fully functional so that if the user
clicks on links within it then control is taken away from my app.

render :file should give me a complete page and the back button will get
back again? but can I also have a close/back button

Is life easier if I call the file .rhtml rather than html?

Bonus question: is it possible to present a scaled view of the page,
e.g. as a mouse hover action.

Pointers to relevant documentation or howtos greatly appreciated