When you visit the building you will see the contrast in the stone colour between the front and back of the building. Also the actual style of construction appears somewhat different between the new and old parts of the building.
Side view of the basilica
Side view of the Basilica.
Gaudí played an active role in directing the construction of the Sagrada Familia until his death in 1926. He would often request that work be modified and adjusted until it was exactly what he had in mind. However today, because of the nature of the existing designs, his work is partly open to interpretation.
Interpretation of the designs by present day architects is particularly challenging because the actual construction stones are irregularly shaped.
The building is still under construction so be prepared to see a lot of work continuing when you visit. However this in itself is interesting, especially if you visit the museum inside the building.
Regardless of all the controversy surrounding the Sagrada Familia it is a truly magnificent building and an absolute must-see when you visit Barcelona.