Black Forest has always been my go-to place to make my main "base", by digging out underneath the Elder altar and essentially giving a completely safe, and fairly large area to set up. I have never had a single mob, including during events, get inside or damage anything inside my home. I have only one portal under there which leads to a larger portal "hub" built at the Boss stones (starting area) where i place all my other portals as well as gardens for growing crops (meadows)

https://steamcommunity.com/sharedfiles/filedetails/?id=2643985164

https://steamcommunity.com/sharedfiles/filedetails/?id=2643985888

https://steamcommunity.com/sharedfiles/filedetails/?id=2434836833

https://steamcommunity.com/sharedfiles/filedetails/?id=2643986196

https://steamcommunity.com/sharedfiles/filedetails/?id=2643986592

https://steamcommunity.com/sharedfiles/filedetails/?id=2434836940

Plenty enough room down there to place all my early-midgame crafting stations and storage, and all completely safe from mobs.