An Introduction to Euclid's Elements
If you spend some time with this interactive site you could discover many geometrical properties. The goal of the author of this site is to stimulate your interest in the subject.
http://mathworld.wolfram.com/Elements.html

Euclid
Euclid is one of the most famous mathematicians from antiquity. If you want some additional information you can check out this site.
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Euclid.html
You might be interested is seeing a page written in the year 888.
http://www.lib.virginia.edu/science/parshall/elementsamp.html