Originally posted by Rhapsody:

Seekers and bats may be able to fly over the dirt walls regardless. IMO if you want a nice looking base, it calls for a moat instead of dirt walls, or just regular walls made of stone and reinforced with iron beams or cages. Multiple separated layers of defense can also be effective, but the best way of dealing with events is to lure the enemies away from your base.

Yeah, i'd say a moat or modify a small offshore island into what you need it to be.