I have this website which decides on the display language by a GET parameter.

http://www.mysite.com/index.php?page=home&locale=en

which is rewritten as

http://www.mysite.com/en/home

When no language is specified, the system defaults to English (en). Now how do I tell the search engines that many versions of the website exist? When the search bot enters the site, it will trigger the default English Language and after finishing, will just leave the site without considering other languages.

I can very well have a sitemap with links to the default pages of each language, so the bot can navigate from there.

But how do I say the bot that the entry in the sitemap is the home page for that language? Like if someone searches for 'mi sitio', they should be presented with the result http://www.mysite.com/es/home and not some other internal page.

Any light on this? Thanks.