On remembrance... And communication

In May I went to Berlin for a few days: I had a very pleasant time, and I thought I would now upload some photos that I took while exploring this lively city. Digital cameras are wonderful, but they do make it easy, far too easy to generate photos that rapidly add up to embarrassingly high numbers. For this reason, identifying a theme and selecting the few snapshots related to it seemed a quite reasonable strategy here. :)
The two pictures above show two memorials: the first one is found in the very central Bebelplatz and commemorates the - sadly famous - book burning ceremony that took place in 1933, while the second marks the spot where the body of Rosa Luxemburg was thrown into the Landwehr canal in 1919.
I have always thought that the choice of empty bookcases to remember a book burning episode is very meaningful. Absence is often regarded as a "lack of presence" and thus seen as a negative condition - yet an absence may be as significant as a presence, in a way which turns out to be much more intuitive than one may expect at first. A quote from Heinrich Heine is engraved next to the glass plate: "Where they burn books, they ultimately burn people".
Since I included a quote, why not add another one? This time it is by Rosa Luxemburg: "Freedom is always the freedom of the dissenter [the one who thinks differently]". The paragraph from which this sentence was taken can be found here: http://en.wikipedia.org/wiki/Rosa_Luxemburg.

This collection of concrete slabs of variable height is known as the Memorial to the Murdered Jews of Europe. It was, and probably still is, a rather controversial project. I must say, I hesitated before I decided to visit it (also, I didn't go to the museum built - literally - under the memorial): even when I was there, surrounded by these grey blocks, my attention was mainly driven towards the construction itself - namely its spatial, geometrical features: light and shadow, uniformity, contrasts, loss of direction.

A memorial, whatever its form and nature may be, cannot provide a single, well-defined and universally (so to speak) accepted meaning: every individual will react differently to it and will be left with a handful of thoughts and impressions. As much as this may sound as an attempt to undermine the value of such monuments and sculptures, I believe it is not so.
Also, I think that an important aspect is their accessibility: anyone walking around Bebelplatz has a chance to see those white, empty shelves. I guess that a similar attempt to "bring a message to passers-by" has inspired science fairs and festivals organised in public squares, for instance: such initiatives are based on the line "If you don't come look for me, I will make myself almost impossible not to be noticed". The question is then: once you are indeed visible, will you be able to speak clearly, and will both parties understand each other? A sparkle that bursts communication is not overly complicated to generate. The point is: what follows the spark, and how?