I started my own Mega park. To be honest i have found this in my old saves from i think a year ago.
I am using custom scenery for some parts and i will add much more hills later on. the castle is just the entrance area. The park is being build by me alone, no servers.
Please note that i may lose interest in RCT2 someday, my interest just jumps everywhere... Anyways, here are some pictures showing the current state :
There are still things i plan and hope for. I especially hope that the Open RCT2 devs will soon be able to remove the attraction limit.