String theory is the leading contemporary framework to explore the synthesis of quantum mechanics with gravity. String phenomenology aims to study string theory while maintaining contact with observational data. The fermionic $Z_2\times Z_2$ orbifold provides a case study that yielded a rich space of phenomenological models. String theory in ten dimensions gives rise to non--supersymmetric tachyonic vacua that may serve as good starting points for the construction of phenomenologically viable models. I discuss an example of such a three generation standard--like model in which all the moduli, aside from the dilaton, are frozen. The M\"obius symmetry may turn out to play a central role in the synthesis of quantum mechanics and gravity. In a local version it plays a central role in string theory. In a global version it underlies the Equivalence Postulate of Quantum Mechanics (EPOQM) formalism, which implies that spatial space is compact. It was recently proposed that evidence that the universe is closed exists in the Cosmic Microwave Background Radiation.