Nurse Wetlands
In Episode 58, Mum Mew announces that the Searchers are leaving Papas and entering a giant marsh, a massive swampy area covering the lower part of Bubalook Island. Since there are so many dangers, the only known ways to get across the wetlands are by an iron bird or by a taxi.

The Wetlands are rumored to be home to a long, scaly beast (presumably some type of Dragon), but actually contain the ruins of an old castle. It takes the team nearly a day and half journey to get across.

In My Monster Rancher, these wetlands are finally given a name: The Nurse Wetlands, the location of several significant battles.