I'm planning to have a trip to China (west & south parts) in Dec 13/Jan 14 for 7-10 days. Could you

I'm planning to have a trip to China in Dec 13/Jan 14 for 7-10 days. Could you recommend some attractive/worth-to-visit places in West and/or South parts of china (as west and south of china are not that cold during winter season) where conveniently assessable by high speed train?