Where is the gitlab webroot?

I am working on getting a ssl cer from lets encrypt but the challenge will fail if it cant find the file example.com/.well_known/acme_challenge/<a bunch of letters and numbers>, and since I dont know where the webroot this will continue to fail. So anyone know where it is?

This path worked for me on Ubuntu 14.04

/opt/gitlab/embedded/service/gitlab-rails/public

thanks