As you may know from research or experience, the best thing you can do for your fluency in a language is to consume large quantities of content that you can understand. (If you are a teacher, the best thing you can do for your students’ fluency is to provide compelling content that your students can understand.) There are lots of ways to make content understandable, but many of them–e.g., looking up lots of words, finding translations, or asking someone else who understands–are tedious, especially if the content is too far beyond your current level.
A fun and efficient way to ingest comprehensible content is to browse websites that present the same information in multiple languages. Many websites have a language selector. Pictured are the United Nations site, which you can read in six languages; the Vatican site, which offers nine (although not all content is available in all the languages); pottermore.com, a leading Harry Potter fan site that comes in six (seven if, as the site does, you count UK and US English separately), and the site of Schola Nova, a multilingual school in Belgium, which can be read in four and whose content I have used with my own students.
Basically, if you know one of the languages and are learning another, you can use the site for language acquisition. Based on your mood, style, and proficiency, you can choose from a few ways of doing so:
1. Read the site in the target language and check your understanding by consulting the site in the known language.
2. First read the site in the language you know better and then read it in your target language. Reading in a language you know constitutes a “pre-reading” activity that gives you a feel for the content and will allow you to understand things when reading in the target language that you wouldn’t otherwise have understood.
3. Open the site in multiple windows, with a different language in each window, to create your own facing translation.
You can get a similar experience by using the languages sidebar at wikipedia.org or, in the mobile version, the “Read in another language” button.
Note that, with Wikipedia, you aren’t getting pages that are translations of each other, but articles written separately in each language, so you might consider this a more advanced tool in which you are getting not only a different language, but also a different perspective. (One might argue that a different language automatically entails a different perspective, but I won’t get into that here.)
You can actually get Google to translate any website, but its translator is too untrustworthy to rely on for language-learning, so I recommend sticking to sites that have created their own versions in different languages and making sure that the language selector doesn’t just use Google Translate to generate the different versions.
See also: The Multilingual Reading Countdown–ideas on a using a similar process with offline content.