Two summers ago, my family and I took a trip to Italy.  While we were there, we spent some time in Florence.  Naturally, we had to visit the Cathedral.  I was surprised and amazed by the sight.  The sheer size of the dome is enough to blow you away.  Add to this the fact that the entire Cathedral is ornately designed and decorated and it becomes one of the most impressive buildings in the world.  More than this, the Cathedral was completed in the 1400s, and is thus a feat of engineering as well.  This Cathedral is a must see for anyone who appreciates great architecture.