Spawn: 61, -30
Igloo: 83, 84
While this world is mostly snow and ice, there are a few forest-covered mountains in you venture far enough out. When you spawn, simply head along the river and you'll spot the igloo on the edge. If you go in and clear away the snow inside, you'll be rewarded with a trap door that leads into a basement.
There's a nice collection of loot down there, so make the most of it before exploring the surrounding area. There are two caged NPCs, one of whom needs purifying before you can free them. There's also a chest with:
Plus, there's a brewing stand with a splash potion of weakness on it.