Palmerston holds a nostalgic place in my heart. Went there quite a few times while growing up in Dumfries and even though the Terregles Street terracing is closed, it still has that old ground feel to it.
Some of these new stadiums can look amazing, but they dont hold the same feeling as the older ones. When you visit an old ground, you get that feeling of it's history and you think about all the amazing things that have happened over the years. I recently read lifted over the turnstyles and while the book is no work of art, it has tonnes of pictures of all of the old grounds in Scotland. Some i hope are never torn down and replaced.
For atmosphere though, I have always like Tynecastle.
The Stadion de Goffert (NEC Nijmegen) was a great experience. Small ground, but cracking atmosphere with a moat around the pitch. Heaters on the top of stands were awesome and certainly kept you warm.