A. The spot where Debra found the truck of "The Ice Truck Killer".

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

A. Somewhere in Miami.

Q. When did we see it on the show?

A. In Episode 2 (of Season 1), "Crocodile".

In the first episode, Dexter had figured out that the killer was using a refrigerated truck and had told Debra.
Dexter later spotted that ice truck, and followed it through the streets of Miami before losing it on a drawbridge.

In this episode, Debra, phones him to let him know that she has found the refrigerated truck of the Ice Truck Killer.

(Debra: "If Miami's the haystack and the ice truck is the needle...  Well, brother, I just found the ####ing needle!")

Dexter shows up and finds the truck sitting, deliberately abandoned, at the side of the road, the engine still running (to keep the contents cold).

Inside the freezer truck, police find a large block of ice, inside of which are "floating" five fingertips, with the fingernails each painted a different color (matching the Barbie doll the killer left in Dexter's refrigerator).

Q. What is it actually in real life?

A. The truck is parked on a public street next to a public park.

Q. Where can I find it in real life?

A. The truck is parked next to Lummis Park & Beach, on the east side of Ocean Drive, in Miami Beach.  That's between 7th Street (on the south) and 8th Street  (on the north).

The truck is parked right across the street from the Johnny Rockets restaurant at 728 Ocean Drive, and near both the Beacon Hotel (720 Ocean Drive) and the Colony Hotel (736 Ocean Drive).

When Dexter shows up, he parks his car on the south side of 7th Street (just a few feet east of Ocean Drive) and walks northeast across 7th Street (then out to Ocean) to join his sister.

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. This was easy.  I had previously tracked down the locations on Ocean Drive.
And the names of the Beacon Hotel and the Colony (and the colorful logo of Johnny Rockets in between), were clearly visible in the background of this ice truck scene. So, I just checked the Yellow Pages for the addresses, then used Google's Street View to verify them.

And Lummis Park itself, of course (which is across the street from those businesses) is memorable enough on its own - boasting perhaps more palm trees per square foot than any other park around...