No no, the MAIN blog :)
The main blog is blog1, but it's the default installation of WP.
So if you install WordPress in domain.com/blogs/, then the main site is domain.com/blogs/ and the subsites are domain.com/blogs/site2 and so on.
But the main blog, in order to not cause wacky errors with the subsites, puts a 'blog' slug before all your posts (not pages, just posts).
Main site: domain.com/blogs
Main site page: domain.com/blogs/pagename
Main site post domain.com/blogs/blog/%permalink%
Sub Site: domain.com/blogs/sitename
Sub site page: domain.com/blogs/sitename/page
Sub site post domain.com/blogs/sitename/%permalink%