In this episode, we visit Pennsylvania to see how engineers are using new technology to fast-track the replacement of more than 500 bridges. Then it’s off to New Orleans for an inside look at the city’s newly constructed $1.1 billion dollar hurricane protection facility. A stop in Seattle reveals how migrating salmon can bypass America’s busiest locks. And finally, a trip to Mexico reveals the ancient symbolism hidden in the Mayan ruins at Chichén Itzá.