Thanks guys, yes it seems I was mixing different grammar paterns.
Statements like こんな綺麗な所は(今まで)見たことがありません. And こんなに綺麗な庭なんて見たことがありません.
Are so handy. I often talk to my friends about shrines or temples I have visited so being able to use these patterns in the past tense can really convey the feelings of admiration, awe, astonishment etc.
こんな見事な寺は(今まで)見たことがありませんでした