Ms Rotterdam in the Norwegian fjords.
Sagrada Familia, Barcelona, Spain
It's the world's most famously unfinished landmark, a Barcelona favourite that attracts millions of tourists every year despite - or perhaps because of - its incompletion. Antoni Gaudí knew it wouldn't be finished within his lifetime but we'll never know whether he would have been shocked or amused by the recently announced estimated completion date: 2028. Don't be put off by the entrance fee to get inside - the wondrous interior is worth every euro.