I did not encounter any toll costs to go up to the dam.. i think the toll is only during summer months.. i will say though the drive up to the dam is not for beginner drivers.. its steep and tight.. on top there is a parking meter now (2 euro an hour).. TIP: go two days you can go left around the lake and you can go right around the lake.. the river on top can be huge giving you no way to cross it.. (as i had in Oct) great place though..