In this unusually shaped puzzle (23x19 squares), six famous bridges are hidden in longer phrases, and their real-world locations are marked in parentheses in the theme clues. The bridges cross unchecked (one-letter) squares in the middle of the grid, and those unchecked squares spell B-R-I-D-G-E.
One note about a pair of adjacent clues: 38D: [Craft seen on game day] is BLIMP and 39D: [Croft seen on game day?] is LARA. I realize the latter is a bit of a stretch since who calls a day that you play video games a “game day,” but it amused me how it could nearly match the clue right next to it, so I went for it.