I received feedback from a teacher about my use of past tense in my diary. I'm not sure where I went wrong here:
I went to see the Osaka castle. It was very beautiful.
大阪城を見に行きました。とても綺麗です。
The teacher corrected me and said it should be とても綺麗でした。Why should we make the sentence in the past tense? Shouldn't the Osaka castle be always pretty (and hence use the term です?)