It's the shortest route to the summit of Peña Negrilla and generally is the first summit before to follow to Moncayo /San Miguel (2315m).
Getting ThereSee the main page to approach to sanctuary of Virgin of Moncayo (1620m). The trailhead is at 500m before the sanctuary in the parking of Haya Seca (1565m).
The route begin in a great stone with some red paint (difficult to read nowadays) following the cairns in the stony path of the forest. The path is good and evident to follow in West direction, even with a little descent in a few of meters. After a hut in ruins we'll exit of the forest in a cross-path. In right side we'll see a path from the track of access to the parking but we'll turn to left in direction to the evident col between the Moncayo (left) and Peña Negrilla (right). After some walks with a lot of vegetation we'll reach the Collado de Castilla (Castilla's col, 1950m, 1h15') with a border-stone.
In the col we'll turn to right side searching some cairns in the wide ramp, with many attention in foggy days, to reach the summit of Peña Negrilla (2118m, 1h45'). If you want is possible to follow 1km to the north to reach the last summit of this area, the Punta Norte (2072m), but you must to return to the main summit the same distance.