This high school geometry lesson, my personal favorite, was adapted from the University of Texas Dana Center. It combines so many geometrical elements: reasoning, proofs, application of formulas, constructing accurate tables, etc. Can be used as a Mid-Term or Final Assessment, depending where you are in your curriculum, small groups or individual. Frankly, I think it's more fun in small groups so different tasks can be assigned to different students. This is a good lesson for all math students, including special needs.
Coordinate Geometry (Using Formulas to determine special quads: Finding Whitebeard's Treasure)