To be held on Sunday 3 July 2011. As well as the marathon, there are half-marathon, 10km and 5km races. More information here.
There is a zipline about 200 metres west of the back gate at the top White Pagoda Hill Park (白塔山). There are photos below, and a promo video on Tudou (which is pretty good, if you can ignore the 'busy' webpage). You can also do a zipline at Xinglong Shan (no photos).
You can plan bus journeys in Lanzhou on Google Maps. Just right click over your departure point and select 'directions from here', then right click over your destination and select 'directions to here'.
The results show a selection of possible routes, how long the journey should take, number of stops, connections, and distances of any walking involved.
Here are the search results for the journey from Lanzhou Station to the Gansu Provincial Museum, with the route used by bus #1 highlighted. Select 'view larger map' to see in full: