Park in the car park behind the citadel of Corte.
(S/E) Take the Mare à Mare Nord trail to the crossroads with the trail to the arch.
(1) Turn right towards the Arche, do not turn left towards the Rossolino Tavignano footbridge. Simply follow the orange trail markers 20 metres north of the Tavignano Gorge until you reach a gate, which you must go through. Then walk along a wall, turn right, climb up a rocky slab and follow the orange markings on the ground. You will only find a little shade further up, before arriving at a small wooded area (chestnut grove).
(2) It takes about 30 minutes to climb up to the Corbaghiola cross (altitude 1,145 metres) on the left, which marks the end of the hardest part of the ascent.
(3) Then, walk along the ridges before discovering the arch below. To appreciate its beauty, continue a little further to reach its level, so you can see the sky inside the arch.
(3) Return to the car park via the same route you took on the way up (S/E).

Thanks to the author!