Tarski's World is a Turbo Prolog implementation of an AI block worlds. There was a lot of rumor about this type of systems in the '70, whith AI researchers believing that this type of systems could be extended to real world situation. However, this attempt failed completely.

Today, Tarski's World is a nice toy and an exercise in logic programming (Prolog). You can download the source code for Turbo Prolog.