Regarding the grammar, both options are acceptable, so I'd say it depends on what you want to put an emphasis on. I faced the same dilema recently. One of my stories is written in the first person, also in the past tense. The protagonist tells about her life at a boarding school. The boarding school still exists when she tells the story even though she is older now and doesn't go to that school any more, so the question is how to describe the school.
What I did is: Since the story is in the first person, I had her describe the school in the past tense because she is not at that school any more, so the school is a part of her live only in her memory at the time of the narration. However, some characteristics of the school, like some very unique rules regarding the school uniform, are fundamental to the story. Since the school's main reason for keeping those rules alive is long-standing tradition, I had the protagonist introduce those rules in the present tense in order for there to be a sense of continuity. Even though she doesn't go to the school any more, her explaining those rules in the present tense means that she firmly believes that those rules must still be in place.
I hope that helps. This is just an example of what I think is the way to handle this.