The Random Page link allows you to visit a page at Wikipedia chosen at random by our Wikipedia gremlins. To enable this option, follow the Preferences link that is at the top of this and every Wikipedia page. At the bottom of the Preferences page, under "Misc.", check the box next to "Add 'Random Page' link to link bar" and save.
If for some reason you don't feel like doing that, you could also access this via URL.