This is fairly easy in Goat City Bay and you will also be able to net the "A Story About My Elevator" achievement at the same time.
You will want to enable these mutators:
Angel goat and double jump.
You could probably manage without, but it is so much easier if you do have them.
Find the tall building, jump up onto the lower building behind and then jump on the mattress. The second bounce should propel you clear of the pool area, but you should try to hit the fans on this jump. These will bounce you onto the roof.
As soon as you land, the first achievement ("A Story About My Elevator") will pop.
If you jump behind the DJ set, this achievement pops.
Video for help: