Where is Mount Sinai?

Judaism began when Israel stood at Mount Sinai and heard the Ten Commandments. Moses climbed to the top of Mount Sinai where G-d taught him all the commandments and gave him the Torah. Mount Sinai is also the spot of an earlier revelation to Moses and a later revelation to Elijah the Prophet. Where is Mount Sinai? Why was it chosen as the place for Judaism to begin? Is it a holy spot in Judaism?