I just fought several battles where the battlefield included buildings.

For example, my army land blockaded a port, and then the enemy came to relieve the blockade, prompting a batlle where there was the actual port on the map (in the playable area.)

Tip: While it might seem like the Port could be a mini fortress, it's actually not a physical barrier. Kind of cool to see units pass through walls.

I also had some weird effects when I had units in a graveyard - but it did work to block the enemy a bit.

I also had some Roman scum hide in a tiny space behind a huge rock in the corner of a battlefield....the rock was cut by the red lines making them impossible to attack.

I have some nice screenshots, but no idea how to post them.