If I say, "I went to a mountain where I had seen a deer before," it may have the following meanings.
1. I went to a mountain and that was where I had seen a deer before. (It is unknown from the above sentence that that was the only mountain where I had seen a deer before or there were some other mountains where I had seen deer.
2. I went to one of the (several or many) mountains on which I had seen deer before.
Am I right?