If you believe that Julius Ceasar existed, then rest assured, you can know that Jesus existed. The reason I say this is because more information, in the way of historical writings, has been discovered about Jesus than any other Biblical figure! There is a plethora of information about Jesus's life and times, according to archaeologists and historians, though most people don't realize this. If you really want to know more, I recommend that you read, Fabricating Jesus, by Craig A. Evans. Also, here is a short YouTube clip from the author:
Also, I've heard there is evidence for Noah's Ark, though I have not personally looked into it.