Where was ismael slaughtered?

He wasn't slaughtered. Allah(SWT) gave Ibrahim(AS) a dream in which he saw him slaughtering Ismael (AS). The next day Ibrahim told Ismael and Ismael said that if Allah has told you you must do it. So Ibrahim was about to slaughter Ismael and the shaytan told Ismael "why? Why are you letting your father kill you" Then Ismael threw 7 stones at him and the shaytan went. Ibrahim was about to slaughter Ismael when Allah (SWT) sent down a sheep in his place. This happend in Mecca. Thus why on Hajj we throw 7 stones at the shaytaan and slaughter a sheep on the day of eid.