The engineering marvel Machu Picchu sits perched on a ridge in the Peruvian Andes. Originally built by the Incas, this magnificent structure remains a mystery. Was it an observatory? Pleasure retreat? Fortress? This program presents the most current theories.

Winding 6,000 kilometers through undulating mountains, it is said to be visible with the naked eye from the moon. But who called for the Great Wall's construction, and how was it accomplished? Historians, engineers, and scientists explore one of the wonders of the ancient world.

During the Cold War, the Berlin Wall stood as a forbidding barrier in an embattled world. Erected in August 1961, the Wall system stretched 103 miles through and around Berlin, locking in 1.3-million people. 261 died trying to get over, under, around, and through it. We review the daunting devices within the Death Strip--one of the deadliest obstacle courses ever--and the ingenious ways people ran it. When the Wall fell with a thud in 1989, its pieces became souvenirs or were recycled for new roads.

Constructed as tombs for the ancient pharaohs, over 100 pyramids remain in Egypt. Built during a span of well over 1,000 years, they stand as cultural and engineering marvels of staggering proportions. But many things about these monuments, including the exact methods used to construct them, remain tantalizingly obscure. Travel back in time as we investigate their evolution--from the earlier mastaba to the Step Pyramid, Bent Pyramid, and of course, the magnificent necropolis at Giza.

The remarkable story of how the landmark New York City skyscraper was constructed during the depths of the Depression. Requiring 10 million bricks and 60,000 tons of steel beams and using a revolutionary technique to hold the steel girders in place--hot rivets--the world's tallest building was completed four months ahead of schedule.

San Francisco's Oakland Bay Bridge stands as an incredible feat of engineering against the nearly impossible. Once chosen as one of the seven engineering wonders of the modern world, it features a unique double suspension structure in its west end. Join us as we cross this triumph of construction, while we visit its past and look to its future.

Join us as we span the history of one of the world's most famous bridges, London's Tower Bridge. The world's largest bascule bridge (a counterweighted drawbridge), when it was erected in 1892, it became a postcard image of London. The famed gothic towers of this pioneering steel structure, sheathed in stone, are purely decorative.

Under Athens' bustling metropolis, a unique engineering project transformed the city, building a new underground Metro system, uncovering secrets of its past, and alleviating chronic traffic problems.

The engineering marvel Machu Picchu sits perched on a ridge in the Peruvian Andes. Originally built by the Incas, this magnificent structure remains a mystery. Was it an observatory? Pleasure retreat? Fortress? This program presents the most current theories.

Winding 6,000 kilometers through undulating mountains, it is said to be visible with the naked eye from the moon. But who called for the Great Wall's construction, and how was it accomplished? Historians, engineers, and scientists explore one of the wonders of the ancient world.

During the Cold War, the Berlin Wall stood as a forbidding barrier in an embattled world. Erected in August 1961, the Wall system stretched 103 miles through and around Berlin, locking in 1.3-million people. 261 died trying to get over, under, around, and through it. We review the daunting devices within the Death Strip--one of the deadliest obstacle courses ever--and the ingenious ways people ran it. When the Wall fell with a thud in 1989, its pieces became souvenirs or were recycled for new roads.

Constructed as tombs for the ancient pharaohs, over 100 pyramids remain in Egypt. Built during a span of well over 1,000 years, they stand as cultural and engineering marvels of staggering proportions. But many things about these monuments, including the exact methods used to construct them, remain tantalizingly obscure. Travel back in time as we investigate their evolution--from the earlier mastaba to the Step Pyramid, Bent Pyramid, and of course, the magnificent necropolis at Giza.

The remarkable story of how the landmark New York City skyscraper was constructed during the depths of the Depression. Requiring 10 million bricks and 60,000 tons of steel beams and using a revolutionary technique to hold the steel girders in place--hot rivets--the world's tallest building was completed four months ahead of schedule.

San Francisco's Oakland Bay Bridge stands as an incredible feat of engineering against the nearly impossible. Once chosen as one of the seven engineering wonders of the modern world, it features a unique double suspension structure in its west end. Join us as we cross this triumph of construction, while we visit its past and look to its future.

Join us as we span the history of one of the world's most famous bridges, London's Tower Bridge. The world's largest bascule bridge (a counterweighted drawbridge), when it was erected in 1892, it became a postcard image of London. The famed gothic towers of this pioneering steel structure, sheathed in stone, are purely decorative.

Under Athens' bustling metropolis, a unique engineering project transformed the city, building a new underground Metro system, uncovering secrets of its past, and alleviating chronic traffic problems.

The engineering marvel Machu Picchu sits perched on a ridge in the Peruvian Andes. Originally built by the Incas, this magnificent structure remains a mystery. Was it an observatory? Pleasure retreat? Fortress? This program presents the most current theories.

Winding 6,000 kilometers through undulating mountains, it is said to be visible with the naked eye from the moon. But who called for the Great Wall's construction, and how was it accomplished? Historians, engineers, and scientists explore one of the wonders of the ancient world.

During the Cold War, the Berlin Wall stood as a forbidding barrier in an embattled world. Erected in August 1961, the Wall system stretched 103 miles through and around Berlin, locking in 1.3-million people. 261 died trying to get over, under, around, and through it. We review the daunting devices within the Death Strip--one of the deadliest obstacle courses ever--and the ingenious ways people ran it. When the Wall fell with a thud in 1989, its pieces became souvenirs or were recycled for new roads.

Constructed as tombs for the ancient pharaohs, over 100 pyramids remain in Egypt. Built during a span of well over 1,000 years, they stand as cultural and engineering marvels of staggering proportions. But many things about these monuments, including the exact methods used to construct them, remain tantalizingly obscure. Travel back in time as we investigate their evolution--from the earlier mastaba to the Step Pyramid, Bent Pyramid, and of course, the magnificent necropolis at Giza.

The remarkable story of how the landmark New York City skyscraper was constructed during the depths of the Depression. Requiring 10 million bricks and 60,000 tons of steel beams and using a revolutionary technique to hold the steel girders in place--hot rivets--the world's tallest building was completed four months ahead of schedule.

San Francisco's Oakland Bay Bridge stands as an incredible feat of engineering against the nearly impossible. Once chosen as one of the seven engineering wonders of the modern world, it features a unique double suspension structure in its west end. Join us as we cross this triumph of construction, while we visit its past and look to its future.

Join us as we span the history of one of the world's most famous bridges, London's Tower Bridge. The world's largest bascule bridge (a counterweighted drawbridge), when it was erected in 1892, it became a postcard image of London. The famed gothic towers of this pioneering steel structure, sheathed in stone, are purely decorative.

Under Athens' bustling metropolis, a unique engineering project transformed the city, building a new underground Metro system, uncovering secrets of its past, and alleviating chronic traffic problems.