If we stay several days in Refuge de Poqueira (2500m), a good option is climb one day Mulhacén (3478m) or Alcazaba (3364m) and in a different day the peak Veleta (3396m). It's not a frequented route, generally all the people goes to Mulhacén, and it's necessary the use of map and probably to follow the indications of the keepers of refuge to localize the beginning of the route, but it's the best option in my opinion to climb the two highest peaks of Sierra Nevada in 2 days.
Alternative: the route of Río Seco goes across a path not always evident in the beginning and it exist another route from Refugio de Poqueira. This option is to take the path of Mulhacén to Refugio de la Caldera and before the Col de la Mosca turn to west following the track to the summit. It’s longest and always across the track. I think is reasonable to make this route as descent in the return to Poqueira because the ravine of Río Seco is nicest.
Time: 4h to summit, total 7h
Slope: 1000m (800m to summit but it’s necessary to climb Loma Pelada in the return)
Getting ThereYou have information in the webs of Mulhacén or Veleta
We'll begin in the refuge descending some meters to west to get the path near the river Mulhacén. It's the same to reach the collado de la Mosca and route of Mulhacén. After some meters, in the point what the path begin to ascent we'll see a cairn in the other side of the river in a green hill. We'll cross the river in this important point leaving the route of Refugio de la Caldera and Mulhacén. In the first meters the path is not evident surrounded of green plains but the path appear at last to border the Loma Pelada in the south face to reach the entry of Barranco (ravine) de Río Seco. The path descent now some meters to reach the path over the ravine in an interesting and desolated place. Finally we'll reach the end of the path in a very wide area with a lot of stones. Some cairns are the best help to follow in North direction to the exit of ravine. A very good help in the orientation is the ridge of Crestones del Río Seco (3152m) in front of us. Walking to the North among the stones we'll reach the beautiful Lagunas (lakes) de Río Seco (they are dry in summer generally). In this point we'll exit of ravine to reach the track of Sierra Nevada (between Veleta and Collado de la Mosca). Following the track we'll traverse the collado del Lobo turning under the peak Cerro de los Machos (3327m). We'll follow to S.W. in direction to Refugio de la Carihuela (3229m) and collado del Veleta reaching the entry of normal route from the ski-resort. Now it's the same approach to summit in the wide ramp S.W. of Veleta.
For the return to refuge we can follow the track what we’ve used in the last part to reach Puntal de Loma Pelada (3185m) descending to Laguna and Refugio de la Caldera, using the normal path to Mulhacén to return to the South.