Tour the Solar System! In November of 1997, a unique, educational monument and memorial was dedicated. Built, in part, to honor Ithaca resident and Cornell Professor Carl Sagan, the Sagan Planet Walk is a scale model of the Solar System in the midst of the City of Ithaca, and part of the Sciencenter Museum exhibits. The model starts with the sun at the center of the Downtown Ithaca Commons and stretches north to the Sciencenter ending with Pluto, 3/4 mile, 1.2 km away. On the Discovery Trail.