Cycling routes in Asturias with barely any gradient

Those with easy or moderate-easy difficulty and catalogued as suitable for cycle touring (BTT): they usually have compacted gravel or tarmac surfaces and gentle slopes, such as the Senda del Oso or much of the mining valleys greenways.

Yes, there are bike rental points at the Senda del Oso accesses in Tuñón and Entrago; opening hours and rates change with the season, so it is worth confirming them before you go.