About 4 km from Magaluf, Portal Vells is located in a relatively isolated area, only reacheable if driving a modest dirt road leading you past the Poniente golf club. The beach is about 100 m wide and 20 m long, and the water is relatively shallow.
Portal Vells is a really nice and relatively quiet beach. You'll find small stones in the water right at the edge of the beach, but after only a few meters, you'll reach the most beautiful sandy bottom and very nice water. Quite a few boats sail there, indicating that it's very much considered a nice bay for swimming by both tourists and locals. You can dine at a fine restaurant directly at the beach.
It's a good beach for children and families with children, because there is plenty of room to play in the shade of tall trees, and the water is calm and relatively low. You also have good opportunities for snorkeling.