Why do people deliberately destroy cultural heritage? By doing so, do they believe they're erasing our history? Our cultural memory? It's true that we are losing cultural heritage to erosion and natural disasters, but this is something that is simply difficult to avoid. I'm here to show you today how we can use pictures -- your pictures -- to reclaim the history that is being lost using innovative technology and the effort of volunteers. In the early 20th century, archaeologists discovered hundreds of statues and artifacts at the ancient city of Hatra, in northern Iraq. Statues like this one were found in fragments, some of them missing their heads or arms, yet the clothing that they are wearing and their pose can still tell us their story. For example, we believe that by wearing a knee-length tunic and open bare feet, this was representative of a priest. However, with a closer look at this particular piece, we can see that this tunic being worn was elaborately decorated, which has led many researchers to believe this was actually a statue of a king performing his religious functions. When the Mosul Cultural Museum opened in 1952 in northern Iraq, this statue, as well as others, were placed there to preserve them for future generations. Following the US-led invasion of Iraq in 2003, a few statues and artifacts were relocated to Baghdad, but this statue remained. Then in February of last year, a video was released, and it instantly went viral. Maybe some of you remember seeing it. Here's a short clip. (Video) (Singing in Arabic) (Singing ends) Not a very pleasant sight, right? Did you notice anything familiar in the video? There it is. There is that very statue, as it was toppled over, breaking into pieces. When Matthew Vincent and I saw this video, we were shocked. Since we are archaeologists using innovative technology for digital preservation, an idea sprung to mind. Maybe we can crowdsource the images that were taken of these artifacts before they were destroyed, to create digital reconstructions. If we can do that, maybe we can put them into a virtual museum to tell that story. And so two weeks after we saw this video, we started the project called Project Mosul. Remember the pictures of the statue I showed you before? This is actually the crowdsourced reconstruction of it before it was destroyed. Now, many of you may be wondering, how exactly does this work? Well, the key to this technology is called photogrammetry, and it was invented here, in Germany. It is the technology that allows us to use two-dimensional images taken of the same object from different angles to create a 3D model. I know you may be thinking this sounds like magic -- but it's not. Let me show you how it works. Here are two crowdsourced images of the same statue. What the computer can do is it can detect similar features between the photographs -- similar features of the object. Then, by using multiple photos, in this case, it can begin to reconstruct the object in 3D. In this case, you have the position of the cameras when each image was taken, shown in blue. Now, this is a partial reconstruction, I admit, but why would I say partial? Well, simply because the statue was positioned against a wall. We don't have photographs taken of it from the back. If I wanted to complete a full digital reconstruction of this statue, I would need a proper camera, tripods, proper lighting, but we simply can't do that with crowdsourced images. Think about it: How many of you, when you visit a museum, take photographs of all parts of the statue, even the back side of it? Well, maybe if some of you find Michelangelo's David interesting, I guess -- (Laughter) But the thing is, if we can find more images of this object, we can improve the 3D model. When we started the project, we started it with the Mosul Museum in mind. We figured we may get a few images, some people interested, make one or two virtual reconstructions, but we had no idea that we had sparked something that would grow so quickly. Before we knew it, we realized it was obvious: we could apply this same idea to lost heritage anywhere. And so, we decided to change the name of the project to Rekrei. Then, in the summer of last year, "The Economist" magazine's media lab reached out to us. They asked us, "Hey, would you like us to build a virtual museum to put the reconstructions back inside, to tell the story?" Can you imagine us saying no? Of course not. We said yes! We were so excited. This was exactly the initial dream of that project. And so now, any of you can experience RecoVR Mosul on your phone, using Google Cardboard or a tablet or even YouTube 360. Here is a screenshot from the virtual museum. And there it is ... the partial reconstruction of the statue, as well as the Lion of Mosul, the first reconstruction completed by our project. Although the video doesn't explicitly show the Lion of Mosul being destroyed, we have many other examples of large artifacts being destroyed that were simply too large to have been stolen. For example, the Gate of Nimrud in northern Iraq. This is a digital reconstruction from before, and this is actually during the destruction. Or the Lion of Al-Lāt, in Palmyra, Syria: before ... and after. Although virtual reconstructions are primarily the main focus of our project, some people have been asking the question: Can we print them in 3D? We believe 3D printing doesn't offer a straightforward solution to lost heritage. Once an object is destroyed, it's gone. But 3D printing does offer an addition to tell that story. For example, I can show you here ... There is the statue from Hatra and the Lion of Mosul. (Applause) Thank you. Now, if you look closely, you'll notice that there are some parts that have been printed in color, and some parts that are in white or gray. This part was added simply to hold the statues up. This works the same way if you visit a museum, and a statue is found in fragments; it's put together for the people to see it. This makes sense, right? However, we're much more interested in what virtual reality has to offer for lost heritage. Here is an example of one of the tower tombs that was destroyed in Palmyra. Using Sketchfab's online viewer, we can show that we have reconstructed three parts of the exterior of the tomb, but we also have photos of the inside, so we're beginning to create a reconstruction of the wall and the ceiling. Archaeologists worked there for many, many years, so we also have architectural drawing plans of this lost heritage. Unfortunately, we are not only losing cultural heritage to areas of conflict and at war -- we're also losing it to natural disasters. This is a 3D model of Durbar Square in Kathmandu, before the earthquake that occurred last April ... and this is after. You may be thinking, you didn't create these 3D models with only tourist photographs, and that's true. But what this represents is the ability for large, public organizations and private industry to come together for initiatives like ours. And so one of the major challenges of our project, really, is to find photographs that were taken before something happens, right? Well, the internet is basically a database with millions of images, right? Exactly. So we have begun to develop a tool that allows us to extract images from websites like Flickr, based on their geotags, to complete reconstructions. Because we're not only losing cultural heritage to natural disasters and in war, but we're also losing it to something else. Any idea, just looking at these two pictures? Maybe it's a little difficult to remember, but only a few weeks ago, this was the example of human destruction by human stupidity. Because a tourist in Lisbon wanted to climb onto this statue and take a selfie with it -- (Laughter) and pulled it down with him. So we're already finding photographs to complete a digital reconstruction of this. We need to remember that the destruction of cultural heritage isn't a recent phenomenon. In the 16th century, European priests and explorers burned thousands of Maya books in the Americas, of which we only have a handful left. Fast-forward to 2001, when the Taliban blew up the Bamiyan Buddhas in Afghanistan. You see, cultural heritage is about our shared global history. It helps us connect with our ancestors and their stories, but we're losing pieces of it every day to natural disasters and in areas of conflict. Of course, the loss of human life is the most heartbreaking loss ... but cultural heritage offers us a way to preserve the memory of the people for future generations. We need your help to reclaim the history that is being lost. Will you join us? (Applause)