There are two icons with 'steps'.
The one with the gray arrow, like on the Fortified Farm, means that the building is an Elevated/Dominant Position.
The other icon, with a blue arrow, is called Stairs, explaining that a building has multiple levels. There's also a separate icon for levels, see below.
These rules for Dominant Positions are in the Compendium and also in a few other expansions. I have to check when I'm at home. The explanation in the Compendium even uses the Fortified Farm as an example.
The Fortified Farm is an older building, from 2013, and I think it's a multi-part building, where you can destroy the tower separately from the rest of the building. Later on, there was an icon that indicated floor levels (like in the Lighthouse in the Pointe du Hoq expansion for example), which makes me think this Fortified Farm could be played as a two-story building too… but that's my interpretation, nothing official.
|