It's actually called "Within the walls of Eryx" or (more often) "In the walls of Eryx", but I like the less common title better...
There's a wikipedia
entry on it, and the text is pretty easy to find on the internet.
It's a less-known story, partly since it is one of Lovecraft's many collaborations (with Kenneth Sterling), and partly because it is a almost entirely straight sci-fi piece, rather than an Eldritch horror like so much of HPL's work.
It took a LOT of adapting, since the story runs as a series of log entries of the protagonist, Kenton Stanfield, that take place while he is entirely alone out on the "jungle planet Venus" (the story was written in 1936, when this was the common belief).
Lovecraft is always a pain to adapt for audio, since he never writes dialog, and dialog is the mainstay of audio. "The Temple", the next Lovecraft I have recorded and will master up for next year, was the same way - a series of log entries of a U-boat commander in WWI.