Multi Site base url question

I am looking for a way to use the bloginfo() code to retrieve the multi site base url. Say if I have the base site “/” and a sub directory site “/blog-one” and want to link to the base site url using bloginfo from the sub directory site.

If I use:

<?php bloginfo ('url') ?>

in the “/blog-one” site it will link me to “/blog-one” not “/”. Is there currently a way to do this without using a direct path? Thanks so much if you can help.