Stopover 4 nights in Beijing. Need a transit visa?

Hi, I am going to stay in Beijing as a stopover for 4 days and then travel on. During this time I want to see the great wall and other scenic spots around beijing. My question is do I need some sort of visa for a short stay like this? Or am I always allowed to stay at least 7 days uppon arrival, or do I have to apply for a tourist visa ?

Greatful for an answer
Stina from Sweden