It's somewhat obscured by TVMs now, but if you go down the stairs, you'll see this sign.
Following it takes you down this half-painted tunnel, then down this path.
And you end up here! An entrance to the Olympia Fields Country Club. I'm not a member so I can't go in, but it looks alright from here.
On the other side is the post office, which looks pretty neat. The zip code's also close to a Chicago zip code - 60461, instead of 60641.