Questions & Answers about Туристический автобус стоит у вокзала.
Вокзала is in the genitive singular case.
The preposition у (meaning at, by, near in this sentence) always takes the genitive:
- у вокзала – by/at the station
- у дома – by/at the house
- у реки – by the river
So once you choose у, the noun after it must be in the genitive: вокзал → вокзала.
Both can be translated as at the station, but they feel different:
у вокзала – literally by the station, usually outside or right next to the building/complex.
- Туристический автобус стоит у вокзала.
The bus is next to the station, probably outside.
- Туристический автобус стоит у вокзала.
на вокзале – at the station in the sense of on the territory / in the station area (inside the building, on the platforms, etc.).
- Я жду тебя на вокзале. – I’m at the station (inside/within it) waiting for you.
So у вокзала emphasizes near the station, while на вокзале emphasizes being on/within the station area.