The Sagrada Familia
There doesn't seem to be a timeline as to when Gaudi's Sagrada Familia will be completed. I first visited it in 1987 when I attended Christmas Eve mass there. Fast forward to 2004, it still had not been completed. Although many changes had occurred and progress definitely evident, what we saw showed a huge gothic style church very unfinished and very much under construction. I just wonder if I'll be able to visit it done in my lifetime.
Bear in mind that the cathedral is so big, it actually has two sides, the old and the new. The old part was designed by Antonio Gaudi himself but the newer side was designed by Josep Maria Subirachs.