Just Observing the Past (The Ultimate History Lessons):
~8500 BC, Atlantis. If it existed, to witness the legendary lost city.
~2580 BC, Valley of the Kings, Egypt. The construction of the Great Pyramid.
May 29, 1453. Constantinople, Byzantine Empire. The fall of the Eastern Roman Empire.
July 4, 1776. Philadelphia, Pennsylvania. The ratification of the Declaration of Independence, and a chance to see a few of my ancestors.
July 1, 1947. Roswell, New Mexico. Find out what really happened.
November 22, 1963. Dallas, Texas. Did Lee Harvey Oswald act alone?
August 15, 1969. Woodstock, New York. The one concert I would travel through time to see.
May 25, 1977. Star Wars on opening day, in any one of the 32 theaters it originally opened in.
September 7, 1978. Louisville, Kentucky. Witnessing your own birth.
May 7, 2005. Cambridge, Massachusetts. The "Time Travellers Convention" at MIT, visiting strictly incognito for the amusement factor.s.
Changing the Past (a.k.a. Fun with Paradoxes):
Use modern weapons, technology and science to ensure that the Roman Empire never fell, and the Dark Ages never happen.
Making sure that Hitler died in battle in WWI.
Visiting myself when I first went to college, and giving myself a few key points of advice.
September 11, 2001. Some things should never have happened.
Going back several years to when the Powerball was at $200,000,000+ with no winners, and give myself the winning numbers (Cash Option ~$80,000,000). With that money, among other things, set up the best outfitted fantasy larp ever and maybe buy the rights to D&D
