I was wondering if there's anything to Mythology at all or was it all made up?

Well of course some of it is real places, events, even people, it's not fiction but archaic dogma that has for the most part we have outgrown altogether. If it's mythology that means that people actually beleived it was the truth at some point.

Ask yourself what you have first hand knowledge in knowing what is real. Hercules was just as real to the ancient Greeks as Jesus is to us today and I Beleive he is just as real as Jesus and I do beleive in Jesus. Someday the legend of Jesus will be a myth. Stories get tarnished and obscured with each passing generation, the story gets twisted over time as people color it for their own personal gain or lack of accurate detail. Flying saucers and little green men are only a myth to those who have not seen them. Someday the holocost may become a myth.

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Here is the 'Gates of Hades', many a Greek hero entered these gates to contact the dead.

Its near Naples, I've been there.

Theres an underground river just as depicted in mythology as being the river Styx.

The Gates of Hades hasn't all been excavated yet, the Romans so feared the place that they filled it in.

There are small islands off the coast of Greece where folklore has it that there lived one eyed giants. The one eyed giant, the son of Poseidon, Cyclops was mentioned in Homers Odyessy.

Some paganists like Alistair Crowley, claim that they can summon up the Olympian 'Hermes'.

How much of mythology is made up?

Who cares, just relish in your imagination and wonder, best it stays a mystery.

Not according to the dictionary