A. A crime scene below a split bridge.

Q. Where is it supposed to be on the show?

A. In Miami.

Q. When did we see it on the show?

A. In Episode 2 (of Season One) - "Crocodile".

Dexter arrives at a crime scene beneath a split (two-span) traffic bridge. He finds the body a man lying dead on the ground, his head smashed from a fall from the bridge above them.

It turns out that the dead man was a policeman who had been working undercover, passing as a mob member. The mob found out his secret and pushed him off the bridge ("the westbound causeway", Dexter says, "not the eastbound.")

Upon closer inspection of the corpse, Dexter finds a round, flat piece of human flesh inside the dead man's mouth. (Later, it turns out to be from the arm of the mobster who killed him - who apparently was bitten during the struggle).

Q. What is it actually in real life?

A. A flat, open area below a bridge.

Q. Where can I find it in real life?

A. The split traffic bridge is the MacArthur Causeway, the east side of which links the Miami mainland with Watson Island in the Biscayne Bay.

The spot where the policeman fell is under the bridge, on Watson island, where MacArthur Causeway first passes over the eastern edge of the island.

The Miami Children's Museum (at 980 MacArthur Causeway) is located just 1,000 feet south of the spot where they filmed the fallen policeman. Jungle Island (an animal theme park), also on Watson Island (at 1111 Parrot Jungle Trail), is a similar distance to the west.

Here is an aerial photo of the location, with the key locations marked. And here is a map link.

Q. How the heck did you figure out where it was?

A. I was temporarily thrown off the hunt by a red herring. The opening shot of Dexter eating a banana while driving over a bridge is not the same bridge.

Once I realized this, I went back to the only split bridge in the Miami area, the MacArthur Causeway, and used Live Local aerial images to examine it closely, to check to see if the view of the mainland corresponded to the screenshots as well. It all matched up. It was clear that the scene was was shot on the plain gravel-strewn area under the west end of the bridge, because the land under the east end has a grass lawn.