Picture environment “rotating” text

I'd like to know how can I rotate text in the picture environment.

I want to typeset some text from bottom-to-top, making it to appear sideways.

Basically, the following

\begin{picture}(...,...)
\put(0,0){\rotate{-90}{Text.}}
\end{picture}


should be printed like

(The text's background is gray, because it's funnier that way!)

-

You could use rotatebox from the graphicx package.
\documentclass{article}