I've seen this movie on TV when I was small. I couldn't remember the story's premise except for the fact that it was a Blob like creature that grew when hit with radio activity. Recently, thanks to the internet, I got to watch this movie after so many years, and was surprised to find that archeology was the basis of its sub plot.
Archeologists goes on an expedition to a cave near Mayan ruins of Tikal, and accidentally discovers the monster Mayans associated with goddess Caltiki. Piece of Caltiki arrives back in Mexico city with the scientist which it tried to consume. Meanwhile, a comet is due to pass close to the Earth - the same comet passed near the Earth at the time the Mayan civilization mysteriously collapsed. Will Caltiki rise again, this time to end our civilization ?
Seriously, this is one of the best sci-fi movie from the late '50s. I saw this movie before I saw Steve McQueen's "Blob", and the Blob was somewhat lukewarm compared to Caltiki. There's been many movies featuring slime monsters, but this in my opinion is the best. The movie has the monster placed in middle of a pretty serious background where all the actors and scenery looks real. This is what makes this movie extra creepy, and also interesting to watch. To categorize this as a common B movie don't do justice. One of the better movie from the '50s.