Этот гид работает во дворце днём, а вечером водит туристов по набережной.

This guide works in the palace in the daytime and in the evening leads tourists along the embankment.

Breakdown of Этот гид работает во дворце днём, а вечером водит туристов по набережной.

• по: along
• вечером: in the evening
• турист: the tourist
• этот: this

Questions & Answers about Этот гид работает во дворце днём, а вечером водит туристов по набережной.

Why is it во дворце and not just в дворце?

Russian has two forms of the preposition в: short в and fuller во.
You use во mainly:

• before some words starting with two consonants (especially when the first is в or ф) to make pronunciation easier:
  • во Франции, во втором ряду, во флоте
• sometimes just by tradition / euphony, even if в is technically possible.

With дворец the standard, natural form is во дворце.
в дворце is not wrong grammatically, but it sounds awkward and is almost never used in normal speech.

What case is во дворце, and why do we use that case here?

во дворце is in the prepositional case (singular).

The verb работать answers the question где? (where?) when talking about place of work, so it takes a preposition of location (в, на) + prepositional case:

• работать в школе
• работать в офисе
• работать на заводе
• работать во дворце

So дворец → во дворце (prepositional) means in the palace as a location.