Resurrect a 5 year old topic to add nothing but silliness? Great work folks.
Its been possible to make cave entrances - including removing collision - since ue4.11 at the very least.
Look up tutorials online, there’s bound to be only about a billion.
Extrapolating from how you do it manually, to creating and setting up a render target to drive the actual landscape in real time takes maybe 10 minutes.
Anything that is driven by the material itself can happen in real time.
Anything that’s done by sculpting tools cannot.