I am (just) old enough to remember the fall of the Berlin wall. When I was little I assumed that Berlin coincidentally spanned the line dividing East and West Germany, and that the wall was part of the longer national boundary - so it came as some surprise to see it on a map, some time after the reunification, and learn that West Berlin was actually quite far inside East Germany.
Most of the wall has been torn down, and Berlin today doesn't feel like a divided city. Most of the way, the route of the wall is marked only by a line of cobblestones (bottom photo), but at Bernauer Strasse there's a great memorial area where you can see a stretch of surviving wall. There are also a number of information boards, giving the history of the wall and its development. I'm not ashamed to say that I cried a little, reading so many stories of how people were affected. One of the great strengths of this exhibit is that it gives you named individuals and detailed accounts of escape attempts, not just dry facts and figures. Very sad and sobering to think that this was going on so recently, even in Europe.
Standing with one foot on either side of the boundary, I was glad that I could do so - but it felt very strange to think that such a thin barrier kept a nation divided for so many years.