Chase taxi.

You catch up to the vehicle, only to discover it's the one you already decided not to take earlier. Nevertheless, the driver looks perfectly normal (well, for a taxi driver, anyway) and doesn't seem to bear you any grudges for your having implied he was a psychopath by rejecting him before.

You can:

Swallow your pride and take the taxi after all.

Apologise to the driver and walk to your hotel instead.

Suddenly run off down a narrow street heading for the opera house. This crazed taxi driver is clearly stalking you...