Look for another taxi.

You ignore the taxi, to the evident disbelief of its driver, and walk off looking for another one. It soon becomes apparent, however, that this is a very busy period for taxi. Eventually, however, you spot one heading off up a side road.

You can:

Chase after the taxi shouting, " TAXI!", as loudly as you can.

Give up and walk to your hotel instead.

Head back to the opera house in the hope that the taxi rank there has some taxis in it now.

Look for the nearest underground station and forget about taxis. They only rip you off anyway...