Questions & Answers about Tämä käynti virastossa kesti vain vartin.
Because virastossa is the inessive case (“in/at the office”), describing the location where the visit took place.
- virastossa = in/at the office (where you were)
- virastoon (illative) = into/to the office (movement/destination)
So käynti virastossa is “a visit at the office.” If you wanted to stress going there, you’d more naturally say something like Kävin virastossa (“I went to the office / visited the office”), but with the noun käynti, the place is commonly given as the location of the visit.
Käynti is in the nominative singular. Here it’s the subject of the sentence: the thing that lasted.
The full subject phrase is Tämä käynti virastossa (“This visit at the office”).