Originally posted by CritMasterFlex:

Your wall can be made "taller" by digging down a little bit in front of it. Basically a trench/wall combo that makes the wall taller on the outside.

I mostly do this especially if the perimeter hasn't been flattened and/or too low elevation that moat hits water.

Also I really like the tree idea but rolling them into place is sometimes difficult as they are so fragile. You have to do lots of hoe'ing and obstacle removal.

There is also the wooden beam approach. Saw it here on forums, can't find the post and picture to reference, but if you have a *very* flat and level perimeter and are *very* careful in placing the 2m long wooden beams, you can create a barrier the mobs can't step over nor hit.

Another approach to defense is to use the various blocking methods in combination with spawn denial so that the shortest paths leading to your base interior passes within bow range of a small 'fort' that is accessible by portal from your base.

Lately though I just use the 'rule of three and forty' (see wiki for event mechanics) and place small satellite farms, ports, whatevers outside the raid range of my main base.