I've been to Barcelona many times on business and never managed to get to see the inside of the Sagrada Familia, so whilst on holiday, I put this right. We had a guided tour as well, which was very informative and well organised. As a non-religious person, the basilica was still amazing. Understanding how the design flows from the old part and the nativity facade (started over 140 years ago) to the passion facade and then the glory facade really put context on the design. As a piece of architecture it really is outstanding in the thought and the design flow. Having done it once, I probably wouldn't go back, but it is totally worth doing once in your lifetime if you are in Barcelona.