KYIV, Oct 6 (Reuters) - A group of people walks slowly in silence past a stand-alone thick wall made of coal with large quartz crystals sticking out of it. People pause to touch the crystals and stand close to the 40-meter-long structure, some with eyes closed. "The Crystal Wall of Crying", an interactive installation by world-renowned performance artist Marina Abramovic, was erected in Ukraine"s capital to commemorate Jews killed in one of the biggest massacres of the Holocaust during World War Two. It will be officially unveiled on Wednesday evening as part of a series of events to mark the 80th anniversary since Nazi troops gunned down nearly 34,000 Jewish men, women and children at the wooded ravine of Babyn Yar on Sept. 29-30, 1941. A symbolic extension of the Wailing Wall in Jerusalem, the artwork is a "wall for healing," Abramovic told Reuters in an interview ahead of the ceremony. "You come here and you look that this is a park. There are so many trees, so much nature, it is so much life. You know, people come here to sit in the sun, little children are playing, but all of this, you know, is one part of reality," said the 74-year-old Serbian artist, speaking in English. "But another part of reality - you know that something terrible, terrible happened at the same time. And that kind of memory can"t leave you. So you have this mix of feeling beauty and heaviness and past which is there all the time." The wall is one of several new installations in a memorial project for Babyn Yar. A synagogue built of wood and designed to unfold like a pop-up book opened in May. read more Abramovic, known for her work with crystals, chose anthracite from Ukrainian mines and rock quartz crystals from Brazil. "I want to create the image that is transcendental about any war at any time at any place," she said. "Whatever we are doing, there is always violence, there is always a war somewhere, there is always something that we should not do as people. And I love to create images that teach us: "stop that"". Editing by Matthias Williams and Gareth Jones