The Sithonia cycling tour is of intermediate difficulty since you cycle on the paved road. Many spots are flat but you do have some climbing to do. The most difficult climbs are between Kalamitsi and Porto Koufo and south of Neos Marmaras. If you are fit and cycle regularly, these hills should not cause you too much difficulty.
Through out the peninsula are paths that mountain bikers also enjoy, such as the ridge outside of Vourvourou that will gives amazing views from above over Diaporos island. A book about cycling tours in Halkidiki was published in 2006 and there you can find all the cycling trails for mountain bikes and the details with maps which we have also included below.