If you didn't get into NYC Marathon but wanted to run a marathon, this is a great marathon. I was Achilles Guide at NYC Marathon so I wanted to run my own marathon two weeks after. Since I live near the Prospect Park it was easy for me to walk to the race and walk home. NYCRUNS does really great job of putting this race together and volunteers are wonderful.
It's three lower part of Prospect Park (2 mile loop) and six whole loop (3.4 mile loop). Both loop has net drop in elevation. If you can managed to run up the Battle Pass Hill (Zoo Hill) of about 0.5 mile, rest of the whole loop is easy mostly descending except some rolling hills after the Zoo Hill.
You can park anywhere around the park since it's on Sunday. Also, there are lots of vacancy after NYC Marathon at hotels where many discounts to be had. Head over to the Park Slope neighbor or any neighborhood surrounding the park for foods from over 50 different countries.