We've been making a list on discord of some of the mountains that have been built. Here's the list below: (I recommend Sourland, Village Des, YMP City & Rockvail Ridge as some of my fav's.)

jaxblax89 - realistic resort v7
diablo - Mount Kushmore Beta055
Smagsy Mt Barker
Smagsy Mt Carru
Jfgx4 mtn creek south 4
Fat_boyfriend Bad Mountain v4
Nivek Chartreuse Backward 6
Nbd19 - Brighton Mountain
pdirty808 - Shredtopia
Scottyhi897 - O'Lad Summit
Kaffeebohnson - Private Property keep out V2
BeardedNAngry - Sketch Park Dusk mod
Jake - Mt hallowsquad
ThelegitCanadian MT YMP Slayer
ThelegitCanadian YMP City V8
Boondocks Dreamland
Jean Olive Village des Pyrenees v.2
M J - Sourland
Notoriouszap - Killer Hill 2.0
MikeDanHan - Rockvail Ridge V4
Chauced - Chauced's Toats Dece Mountain
Hammertime - Mtn. Backwoods V3
Smagsy - Mt3 v3 1
BertMcCert - Shredhead
HotDogn4Life - Agro Crag
MAG1982 - Giants Fork
NumerousMarix - Silver Haze Mountain
Pyscho Mantis - The Camp
Shroud The Wicked - Real Snow Seymou