next and nearest

1. Nearest is used for place - it means 'most near in space'

• Excuse me. Where's the nearest tube station?
  (not... the next tube station?)


• If you want to find Alan, just look in the nearest in the pub.

Next is usually used for time - it means 'nearest in the future'

• We get off at the next station (=the station that we will reach first)


• I'm looking forward to her next visit.

2. We use next in a few expressions to mean 'nearest in space'.
The most common are next door and next to.

• My girl-friend lives next door.


• Come and sit next to me.