48 hours layover - Guangzhou and Beijing

Hi,

I'm a Canadian Citizen. I'll be travelling from Nepal to Beijing with a connecting flight from Guangzhou (Kathmandu > Guangzhou > Beijing). I'm planning to exit the airport in Beijing to do the layover tour. My departure in Beijing back to Canada is on the next day (total stay in China is about 45 hours). My departure is Beijing > Guangzhou > Canada.

Questions:
1. Do I need a visa in advance or does the 72-hour visa-free transit applicable, and where to apply?