About the site:
Yitzhak Rabin Memorial site is located under the Tel Aviv municipality building, close to Rabin Square.
You can see the stairs from which Rabin stepped down, after a peace rally in the square, the assassination took place at the base of the stairs.
You will find the rocks monument, plaques commemorating the event, a statue, and also graffiti.
About the cache:
You are looking for a true nano magnetic, under the bench in the north-west corner, north edge. Precise directions due to heavy security here.
Sit and reach, be very stealthy, as usually place is busy, and there are cameras though none is pointed at GZ. Stay a couple of minutes after placing back. Probably easier at night. Coords may be off here, since it is between two buildings. On my map it looks like cache is inside Gan HaIr building, but GZ is between the buildings.