Lôn Eifion is a 19-kilometre traffic-free cycle and walking path that runs south from Caernarfon along the trackbed of the old Caernarfon-to-Afon-Wen railway. It is part of National Cycle Route 8, the Lôn Las Cymru, the spine route running the length of Wales.
The route is flat or gently downhill heading south, with views of the Llŷn Peninsula to the west and the Eifionydd hills to the east. You can ride to Bryncir or all the way to Bryn-y-felin, with cafés along the way. Bikes can be hired from shops in town. For a half-day return trip, ride out to the Inigo Jones slate-works near Groeslon and come back.