The locations containing the area cards have a "+1 denarius" symbol for the advanced game.
When the area card is up, this is clear: you pay 3 denarius instead of 2 to be able to perform the action and buy the card.
However, what happens when the card is down? Do you have to pay 1 denarius to be able to perform the action?
I did not see this explained in the rulebook but, since the "+1 denarius" symbol is visible even if the card is down, there must be a reason for it...
The rules says you pay 3 in the advanced game for the area cards.
The only reason the icon is there to be consistent with the iconing for the advanced parts. You pay the same way as in the basic game