"The Hole in the Hole" by Terry Bison (ISFDB). Summary from here:
"Sci-Fi author Terry Bisson wrote a humorous short story called "The Hole in the Hole" in which the main character discovers a portal that opens onto the surface of the moon in a junkyard. He and a companion attempt to retrieve the lunar rover so they can sell it for a bundle."
(chelymorpha 5/10/2007 9:13:55 PM)
From the story (accessible in the first link):
There was a cool breeze and a funny smell. Behind me I heard a steady pop, pop, pop. But when I finished and took the brake parts to Frankie, the pile of tires was still the same size. Frankie was on top of it, leaning on the fence, talking with an Indian man in a Goodyear shirt.
The Indian (who must have been standing on a truck on the other side of the fence) saw me and ducked. I had scared him away. I realized I was witnessing some kind of illegal dumping operation. I wondered how all the junk tires fit into the tiny shed, but I wasn’t about to ask. Probably Frankie and the old man took them out and dumped them into Jamaica Bay at night.
“Wu,” I said, as soon as Frankie had left to find his uncle, “let me tell you something about junkyard men. You can’t say ‘I’ll take it, I’ll take it’ around them. You have to say, ‘Maybe it might do, or . . . ’”
“Irving!” Wu cut me off. His eyes were wild. (He hardly ever called me Irving.) He took both my hands in his, as if we were bride and groom, and began to walk me in a circle. His fingers were freezing. “Irving, do you know, do you realize, where we just were?”
“Some sort of cave? Haven’t we played this game before?”
“The Moon! Irving, that was the surface of the Moon you just saw!”
“I admit it was weird,” I said. “But the Moon is a million miles away. And it’s up in the . . . ”