Hi, There are scads of things to do of course!!
I usually have them make pie (extra credit) for us to enjoy while working on a project from Archimedes, or the Babylonians.
Archimedes used inscribed and circumscribed polygons to approximate the value of the circumference of the circle, and from there to the value of pi . . . Nothing more than basic trig ratios, and the formula for the circumference of a circle is required.
The Babylonians got really close to "squaring the circle" with a circle of diameter 9 having nearly the same area as a square of side length 8 . . . so to create a visual of that, or to play around with 64 chips to see if they can arrange them neatly into a circle with diameter 9.
I can find my worksheets if you are interested . . . ?
Thanks for the question since I need to be thinking about it myself, as I also teach Honors Geometry.