Ying Yang Drawbridges

When I lived abroad as youngster I always thought drawbridges were only found at castles as protection against batteling armies.

That was untill I moved to Holland...

There I saw drawbridges all over the place as there is a lot of water around. The function as protection against intruders is the same.

I am used to see them by now, but I never ever saw two next to each other like here in the old center of Maassluis.

Even stranger is that they aren't the same color, but opposite.

Felt like Ying Yang to me :-)