I'm experiencing a severe slowdown around the spiral fountain, although everything else so far has been peachy-keen. I expect that something about rendering that mess is causing it. Already tried creating Config.ini with fps=200, and I'm launching from GCT using OpenGL. Has anybody else experienced this? I'm running in a VM, so that could be related.

I've had the same problem with the original game back in the day. With the GOG release (and on my newer system) it's not just around the fountain spiral, bit with bigger areas in general. I've contacted support but in the end they couldn't help and I gave up, slowdown made the game impossible to play.

The game is deeply rooted in OpenGL and some modern day graphics cards are just not supporting OpenGL anymore. If it's not gamebreaking, all I can advise is sticking through the slow parts, it's well worth it.