The Cathedral of St John the Divine in New York is also unfinished, with construction in fits & starts since 1892:
https://en.wikipedia.org/wiki/Cathedral_of_St._John_the_Divi...
Hram Svetog Save (Church of Saint Sava) in Belgrade/Serbia started construction in 1935 and the exterior was finished in 2017. I haven’t been there in several years, but my understanding is that the interior is still being worked on and will continue for some years to come…
So not quite “over a century” but getting close. :)
Imagine trying to get funding today for a building project that is scheduled to be completed long after everyone alive today would be dead. I can’t imagine that being possible. It’s a pity: I wonder what wonders we could have built using modern technology over such a long timescale.