WPML

WPML makes it easy to run a multilingual website with a single WordPress installation. It comes with over 40 languages. You can arrange different language contents in the same domain (in language directories), in sub-domains or in completely different domains.

Boombox_Widgets

After installation and activation, a user will have to customise the look of the language switcher. For that go to WPML => Languages and enable Custom language switcher section

Boombox_Widgets

For more detailed information, please visit WPML page.