Gyeongju - flat enough to bike?

I'll be visiting Gyeongju near Busan and am wondering if it's possible to get around by bike? I'd like to see all of the main sights - lakes, hills, etc and see that even with public transport it can take quite a while.

I looked into private drivers but they're quite costly so I'm considering just walking & taking the bus, or biking if possible!

Any thoughts are appreciated.