Easter Island! Only a 6 hour flight from Santiago...
...but I guess you mean MAINLAND Chile.

The only ones I know about are the geoglyphs in the Atacama at Cerro Pintado, and the site at Monte Verde in the south: http://en.wikipedia.org/wiki/Monte_Verde

I'd be interested to know what you find as we're wondering about going to Chile in the next couple of years (I have a friend moving to Santiago later this year.)