I need an online registration that contains multiple venues for an event
Making a lot of assumptions here ... you could have a single event configured without enabling the location.  Then use a priceset with each item in the priceset matching a location - set it to required.

e.g.
"Select a Location"
Canberra - $75
Melbourne - $75
Darwin - $75

You'll end up with a master list of all registrants, getting a list of registrants by location requires a price set report, either custom or in the Extended Reports extension.