Visa required ????

Hi,
I am Ayon from Bangladesh (Bangladeshi passport holder). I am a student of New Zealand. I will go to Auckland from Dhaka through China Southern Airlines. I have Layover in Guangzhou for 18h 05m. I will arrive Guangzhou around 8.25am and leaves 2.30 am same day.
Can I visit Guangzhou City during layover time?
Do I need Chinese Visas to go for Guangzhou City tours?
What will be the cost for City tours?
Regrads