This lattice is infinte and subdirectly irreducible but the variety it
generates contains only finitely many other varieties, refuting an
old conjecture. Think of this lattice as wrapped around a cylinder
so that the elements at the sides with the same labels are identified.
Note the middle part of this diagrams moves up when going from left to
right so that when it is wrapped around the cylinder it is helical.
View this page in German courtesy of Alexandra Seremina.
This page will have link to various subbranches of lattice theory containing general information and problems.