I know this isn't strictly speaking an answer to your question, as it's about memory rather than history, but from 2014-2018 (the centenaries of the war), the Tower of London hosted what I thought was a stunning memorial to the casualties of WWI. Artists handcrafted 888,246 ceramic poppies - the official number of British and British colonial deaths in the war - and volunteers planted them, so that visitors could begin to visualize the lives lost:

https://youtu.be/iGVPxnxvFgU