Much like 210; 515 is a "code-name" for Eating Out a girl. 5 represents the fifth letter of the alphabet: E; 15 represents the 15th letter of the alphabet: O.
The actual act of eating a girl out is when some one goes down on a girl and licks/sucks/nibbles varied parts of her pussy; usually to make her cum.
Many claim this to be a delicious "meal"; hence the term "eating out".
a rave-esque festival held in the down town area of des moines in the summer. at 515 alive it's likely to find: break dancing, drinking, graffiti, artists, emo kids, mohawks, lesbians, scene kids, drunks, under-age drinkers and DJs.
the name "515 alive" is an attempt to get rid of des moines' "dead moines" reputation.
I got 4 numbers at 515 alive this year, but I really don't remember who gave them to me. woops.