I have a 12 hour wait in bejing on a flight from Melbourne to Milan - do I need a visa

I have a 12 hour wait in bejing on a flight from Melbourne to Milan - do I need a visa to exit the airport to spend day in bejing before catching connecting flight? I am then returning via Bejing 6 weeks later and have the same amount of time and wish to do another day of sightseeing. What is the process required to achieve this?