What is it: It was opened in 1894 to house the Reichstag (the imperial parliament that ruled Germany from 1871-1918). It was closed in 1933 after it caught fire and it sat empty until Germany reunified on October 3 1990. It was restored by the architect Sir Norman Foster and became the seat of the German parliament when it was completed in 1999. 
What's it like: Very imposing. I could bore on for hours about it, because a) I did my dissertation on Unified Germany's role in Europe and b) I visited Bonn when it was still the capital and centre of government so I saw the alternative. I'll cut to my conclusion: I like the Reichstag.  
Where: Berlin, Germany  
When: March 2007 
How: Pete had always wanted to visit Colditz, so we did a tour of former East German cities - we started in Leipzig, then Dresden, and then finally Berlin. We also visited the Berlin Wall (also removed in 2020 edition) and the Brandenburg Gate (435).
Worth noting: It's definitely worth visiting the dome - it's free and you don't need to do the full tour of the building but you do have to book in advance.  
Place in 2015 edition: 221
Did it deserve to lose its place in the 2020 edition: No. It could have moved down a bit but it's an important monument.