Looking up...
二階に上がりました
I went up to the second floor.
The second floor of a building, typically above the ground floor (first floor).
二階の窓から景色が見えます
You can see the view from the second-floor window.
In Japanese, the first floor is called '一階' (ikai), and the second floor is '二階' (nikai).
In Japan, the ground floor is called '一階' (ikai), and the floor above it is '二階' (nikai). This is different from some Western countries where the ground floor may be called the 'first floor'.
Composed of '二' (two) and '階' (floor), literally meaning 'two floors'.
In Japanese architecture, '二階' refers to the floor directly above the ground floor. The numbering system differs from some Western countries where the ground floor is sometimes called the 'first floor'.