Just a short walk from the busy Festival hubs of the Pleasance and Bristo Square, the National Museum of Scotland can be found in conjoined Victorian and modern buildings on Chamber Street. The older part houses natural world, world cultures, art and design and science and technology collections whilst the newer part is dedicated to the history of Scotland from its origins to the present day.
I have written before about my favourite exhibit, but there is so much more to see and all for free. The world collections underwent major renovations between 2006 and 2011 and the result is a visually impressive, informative and interactive experience with not a moth-eared taxidermy subject or illegible label in sight.
The museum is open daily from 10 until 5, with free hour-long guided tours at 11, 1 and 3. During the Festival the museum is also home to a number of free and ticketed events, including pop-up dance performances and late night access; there really is something for everyone.
For more things to do for free during the Edinburgh Festival see here