Infinite Tunnel problems

I don’t know if I am in the right category. but I have a problem.

I have multiple (GameObjects) Tunnels (each one is different) made where a car is supposed to drive through. What I am trying to simulate is that this tunnel is infinitely long.
After placing a new piece of tunnel, the last placed one should be removed.

my problem is that although the last tunnel is not being rendered it is still being kept in the memory, I think

How do I fix this? what am I doing wrong?

Let me know if you need the code because I am not sure if I am allowed to put my code here.

Thank you for helping and reading this.

If you simply destroy that object, it may be exist for some time, until the garbage collector runs.

Thank you so much, this fixed my problem!