[GS] Two Inca Questions

[vorlon_mi]

New to Civ 6, played nearly all the earlier games in the franchise (Civ 2, 3, 4, 5, and BERT).

How does the Inca special ability to build portals through mountains work? Each time I have a builder on a hex next to a mountain, the interface suggests that improvement. I click on it, the mountain lights up, but nothing actually happens. How do I use that? Do I need a certain number of builder charges to do this?

More general question, not specifically linked to the Inca -- If I denounced an AI (for declaring war on one of my pet city states), how do I retract the denouncement later? In this case, the AI succeeded in conquering my city state. I wasn't the suzerain yet, though I was working up to it. I'd like to "calm" the diplo modifiers, but I can't quite figure out if my denouncement will eventually expire after N turns, or does it last for the whole game.

 

[Buktu]

You have to click on one of the highligthed mountain tiles to finally build the Inca tunnel on this specific tile.

And after some turns the denouncement will just expire like a friendship.

 

[vorlon_mi]

You have to click on one of the highligthed mountain tiles to finally build the Inca tunnel on this specific tile.

And after some turns the denouncement will just expire like a friendship.

But when I click on the highlighted mountain tile, it tells me "Mountain - impassable" and the builder doesn't do anything.
Somehow, I'm still missing something.

 

[Buktu]

When you move your builder right next to the mountain and press the button for the Qhapaq Nan you have to left click one of the mountain tiles to build it. So since you can not select the tile for the tunnel by moving onto the mountain you have to select it with a click (while the mountains are highlighted).
The "Mountain - impassable" sounds like the mouseover for the tile for me.

 

[Bibor]

Inca tunnels are built like regular tunnels. The target mounitain tile must be adjacent to the worker.
Unlike regular tunnels, inca tunnels serve both as a tunnel and a teleport. A unit can enter in one and exit in another one, provided both (or multiple) tunnels/mountain tiles are in the same mountain chain.