The Grotto is an expansion to the ranch set inside a (slightly spooky) cave that allows a rancher to care for light-sensitive slimes without the need for a solar screen. Never has a phosphor slime felt so liberated.
Dark and wet, perfect for phosphors. In the center of the Grotto, (which looks like a large cave, with stalagtites) there is a huge gaping hole covered with wood planks (just like the bridges) and you can see a pool of water at the bottom.
Sub Area: Spring Archipelago
This row of islands leads you to Spring Valley. The jetpack is required to navigate the islands.