What to take on the trail
Barcelona's proximity to real terrain catches people out: a morning that starts on pavement can finish on an exposed ridge with a wind that has nothing to do with the beach below.
The essentials
Water, closed shoes with actual grip, sun protection and an offline map. Mobile signal in Collserola is patchy and paper maps are not sold at the trailheads.
For the big days
Add layers, a windproof shell, more water than seems reasonable and a headlamp for anything that could run past sunset in autumn or winter.
What you can skip
Technical boots are unnecessary weight for Collserola or Montserrat. Trail shoes carry you everywhere in this guide outside of a snowy Montseny.