Small little hill on the west side of the canals

Me and Beemer ike went for a little ride this weekend and explored the western canals for the first time. we eventually saw this little hill that looked like it had a very clear cut road leading to the top of it.

As life goes we learned that not all is as it seems. we found the entrance through a little quarry where after convincing the security gaurd we attempted to get to the top.

I got quite close to the top and then encountered two large rocks blocking the "road". couldn't fit through with panniers. Has anyone gone over. i really wantto know where it comes out. i think there is another quarry on the other side as well.