Arrival at Beijing International Airport and departure from the same airport 40h later

Hi,

We are a Spanish couple. We are going to land in Beijing International Airport from Taiwan and 40h later we are going to take an airplain from the same airport for returning to Spain.

Can we use this 72h free visa-transit to get out the airport and visit Beijing during the 40h we have?

If not, what kind of visa we should get?

Thanks in advance!