The Cave 4 cards are placed at the beginning of the game on a per Bergfeld per quadrant. At least 2 fields distance to castle / town / nomadic fields: The following rule applies.
Players have, therefore, an additional special action that can be performed according to the standard rules, before or after the compulsory action: We must put field, a voltage applied to Cave Bergfelder settlement on any (arable) that is adjacent to a cave.
Thus, the player for example have the opportunity to come quickly to a still unsettled quadrant.
In concept, this extension is quite interesting, but I find the price a bit too high (hence the point deduction).
Theoretically, you could also four 1 - use coins as "Cave marker". This would fit in terms of size, are just as appropriate, would be even more stable (as the cardboard markers) and on top of that would be even cheaper = P The disadvantage of this version would be, however, that Euro coins markers of course not entirely, on the other Game material fit.
