What's bigger, better and harder than a marathon?

I found MY answer. I found my "thing" that is bigger, harder, more mentally challenging, and better than running a marathon.
I have always held in my mind this idea that running a marathon or a triathalon would be a HUGE "mountain to climb" so to speak.. it would be my "mission impossible" ........ but .. tonight..
I had a thought come to my mind.......

in my life.... what would be bigger than a marathon........ what would be a something I could do to celebrate my 40th b-day and would be more difficult for me mentally, and physically than training for a long race event..............
I found my answer.
I have my goal.

I am doing my research......... so you will have to wait a bit to find out what it will be :) .......
I must get my plan together and my mind truly wrapped around what i am about to try and accomplish...........it might not seem huge to anyone else........ but to me........its my Mount Everest...

so ..

Stay tuned.........to find out what I am going to be doing.......


in the mean time.........any of you want to guess what it could be?