Output your Rails routes to html. It is automatically opened by your browser, but this option can be disabled.
Add it to your Gemfile and run bundle install.
gem 'html_routes', '~> 1.0', group: :development
rake html_routes
To specify a custom output file:
rake html_routes out=tmp/custom_file.html
If you don't want the output file to open in your browser automatically:
rake html_routes background=true