On this website, you can see a photo of the four black markers at the ash pond near Krema II at Auschwitz-Birkenau:
http://www.thejewishweek.com/features/rabbis-world/yom-hashoah-reflections-2016-5776
I have a similar photo on my scrapbookpages.com website, which you can see below.

Black markers at Birkenau ash pond

My photo of the ruins of Krema II
My photo below shows the ruins of Krema II where the ash pond is located, although the ash pond is not shown in this view. The brick building in the background is the kitchen in the women’s camp.

My photo of the ruins of Krema II
The following quote is from the news article in the link above:
Begin quote
For my column this week, I would like to share with you the comments I made at our synagogue’s annual Yom Hashoah program on Wednesday evening. They are, in every way, what I would want to say to all of you on this occasion…
If the Passover Haggadah, commemorating a historical event that took place thousands of years ago, drove our imaginations with four questions, a relatively meager text and some clever if enigmatic songs, then what might we possibly say about the Shoah that would be adequate to the task at hand?
The quick answer to that question is, of course, nothing– nothing at all. At the risk of descending quickly into cliché, there simply are no words that are adequate to the task of recounting the myriad horrors that were perpetrated by the Nazis and their sympathizers against our people, the Jewish people, simply because they were Jewish. That is the quickest answer to the question, and certainly the most accurate. The problem with it, however, is that saying “there’s nothing to say” says nothing, and the reason why we are here is because of the categorical imperative to say something– to remember what was done to us, and to pass those memories on. We may not be able to explain it, and certainly not understand it or even adequately describe it, but remembering the Shoah is not- cannot- be a silent activity. It demands words, poetry, music, prayer, and yes, silence – all of which we engage in this evening.
Read more at http://www.thejewishweek.com/features/rabbis-world/yom-hashoah-reflections-2016-5776#TjrEeoRTYFRhdDPh.99

My photo of another view of Krema II ruins
Krema II was constructed by the Huta Corporation, according to a design by Architect Georg Werkmann, which was modified by Walter Dejaco.
In 1972, Walter Dejaco was tried in a German court on a charge of aiding and abetting mass murder; he was acquitted of this charge. He claimed that he did not know that the morgue room, called Leichenkeller 1 on the building blueprint, was actually intended to be used as a gas chamber. The undressing room was called Leichenkeller 2 on the blueprint of the building. Leichenkeller is the German word for Corpse Cellar. On the blueprints of Krema IV and Krema V, also designed by Walter Dejaco, the gas chambers are called shower rooms.