I went to the London march (estimated 100,000 people), and hope to write up a proper report at some point when I recover. It was amazing and I'm very glad I did it, but I knew I'd need to collapse in a small heap afterwards so that's what I'm doing.

The NYT have photos of the marches on all continents:

https://www.nytimes.com/interactive/2017/01/21/world/womens-march-pictures.html