The civilizations of the ancient world left behind awe-inspiring examples of their engineering genius. Yet few clues remain to tell us just how, with limited technology, they achieved their extraordinary feats. To uncover the secrets of such Herculean labors, NOVA sent teams of experts to five archeological sites. The challenges? To actually test their building hypotheses- using traditional techniques.

Pyramid takes us to the shadow of the Great Pyramid of Giza, where Egyptologist Mark Lehner, stonemason Roger Hopkins (of This Old House), and a team of Egyptian workers face a daunting task: to build an 18-foot stone pyramid in three weeks, while trying out some clever construction theories.

Obelisk again sends Lehner and Hopkins to the land of the pharaohs, but on a different mission: to show how a colossal obelisk could have been quarried, chiseled, shipped up the Nile, and erected on a base in front of a temple- using only stones, ropes, logs, dirt (and some monumental human effort).

Colosseum travels to the famous Roman amphitheater, whose blood-thirsty audience was once shielded by a gigantic canopy. Historian Rainer Graefe has come up with a design that borrows from the riggings of ancient sails. Will it win out over a more accepted concept?

Stonehenge is one of the most mysterious places on earth, erected by early Britons some 4,500 years ago. Archeologist Julian Richards, engineer Mark Whitby, the intrepid Roger Hopkins, and a band of volunteers give it their best- to move, raise, and cap a Stonehenge-like structure, armed only with Stone Age tools.

Inca kings built their magnificent, earthquake-enduring citadels high in the Peruvian Andes, without benefit of the wheel, iron tools, draft animals, or mortar. A team of experts chip away at some theories- and local villagers create a breathtaking, 100-foot suspension bridge using nothing but grass.