The Brooklyn Bridge, completed in 1883 and designed by John Roebling, is a cable-suspension bridge. There are two towers connected by horizontal cables. The cable lines run to the land, ending at an anchorage. Emanating down from the horizontal cables are vertical cables that hold up the deck bridge. Weight transfers from the cables to the towers, which is then transferred down to the ground. In the building of the Brooklyn Bridge, two large pine boxes, called caissons, were floated down the East River. When the limestone towers began to be constructed on top of the caissons, they sank until they reached the bottom of the river. Workers were able to enter into these boxes to dig into the bedrock to allow the caissons to sink even further and form a solid foundation. They were then filled with brick and concrete. Everything rests, essentially, on these two pillars.
An interesting aside: vaulted chambers were built into the ramped anchorages at the ends of the bridge. Situated within limestone and maintaining a perfect temperature of 60 degrees, these vaults became perfect wine cellars. In fact, the city rented these cellars out to liquor vendors. On the Manhattan-side entry into one of the vaults was a shrine to the Blessed Mother with a statue of Mary. It was called the Blue Grotto.
Saint Catherine of Siena was no stranger to bridges. She invoked the bridge as an image of Christ. Our Lord is the span between heaven and earth, and the soul must traverse Christ to reach God. There are three stairways on this Christ-bridge. One stairway is our detachment from sin, the second is the practice of the virtues, and the third is the loving union with God. May we marvel at Christ, just as we do the Brooklyn Bridge.