The # thing also works across instagram and Facebook, and you can browse sites without having an account for them (great for you social media phobes)
Visit Europe's museums and tweet pictures with the #MuseumWeek hashtag.
This week's themes are:
Monday: #DayInTheLife
Tuesday: #MuseumMastermind
Wednesday: #MuseumMemories
Thursday: #BehindTheArt
Friday: #AskTheCurator
Saturday: #MuseumSelfies
Sunday: #GetCreative