Happy Fourth of July weekend! If you find yourself with some free time in between the fireworks and barbecues, "National Geographic" has an amazing feature on a team of explorers who used 3D laser scanning technology to create a map of some of the world's largest caves in China. The images are stunning. The magazine's website has the scans and even offers a a 3D tour of the caves.

The lengthy article with plenty of video and images is well worth checking out! The journalist who accompanied the scanning team said of mapping of a limestone cave called Titan: "If there is a perfect cave for the fledgling art of subterranean laser scanning, Titan is it. At the center of its massive chamber, slopes covered with rubble and pockmarked with pools creep relentlessly up to twin, 50-foot stalagmites that sit on the very peak of an underground mountain. Place the scanner atop the big one on the right, and you can take in almost all of Titan—about 13 acres, an area slightly larger than Hong Meigui—in a single 360-degree sweep.”

In case you missed it, on Tuesday PBS premiered the first in a three-part series called "Time Scanners," which you can watch in its entirety on PBS' website. The show explores 3D digital preservation. Each episode follows Steve Burrows, a structural engineer known for working on the Bird's Nest Stadium at the 2008 Beijing Summer Olympics, and his team of investigators as they discover the history and scientific secrets of some major landmarks.

This week's episode focused on the Egyptian pyramids: "The team travels to Egypt to scan the pyramids to find out how the necropoles evolved from simple mud-brick structures to the most impressive buildings in the ancient world. They use their laser technology to scan Djoser’s Step Pyramid at Saqqara, Meidum’s collapsed pyramid, the mysterious Bent Pyramid at Dashur and the famous Great Pyramid at Giza, and finally establish the true location of the King’s Burial Chamber in the Great Pyramid."

Next week's subject is St. Paul's Cathedral: "Burrows takes his team of experts to “St Paul’s Cathedral” in London, famed as the location of the marriage of Prince Charles and Lady Diana Spencer. They venture inside the majestic dome to explore its groundbreaking three-part structure; determine how the cathedral’s architect, Sir Christopher Wren, overcame unstable foundations and immense structural forces to support his dome; and investigate how the cathedral survived a direct hit by a German bomb during the London Blitz."

And, July 15, is Petra in Jordan: "For the final installment, the team ventures to Jordan to scan the ancient desert city of Petra. Using 3D laser-scanning technology, Burrows wants to uncover the city’s construction secrets and shed new light on this architectural wonderland lost to the West for more than 1,000 years. How did Nabatean stonemasons carve Petra’s largest building – the Monastery – out of a mountainside? And what lies hidden underneath the city?"

Watch the full first episode here. Subsequent episodes also will be available on PBS' website the day after it airs.