Montañas Vacías (“Empty Mountains”) is an open route of about 679 km and 12,841 m of climbing through the Albarracín, Gúdar and Javalambre ranges, between Teruel, Cuenca and Guadalajara. Nearly 80% of the route is unpaved and it is known as the “Spanish Lapland”.
It was designed by Ernesto Pastor and can be ridden at any time of year, though spring or autumn is usual. A GPX is available on the original page; check the terms of use of the track there.