The Opera House is stunning, both inside and out. It is also very accessible. Several of the "hop on hop off" busses stop across the street. We were there in early June and able to buy tickets about 10 minutes before the tour started. However, there weren't huge crowds. Tours are offered in various languages but only a couple of times a day. During heavy tourist season it would probably be a good idea to buy the tickets earlier in the day. The interior is absolutely beautiful and the guide was very informative. We choose to buy the optional mini opera concert which was delightful.