Ultum Nature Systems or UNS make high quality aquariums with ultra clear rimless glass in many different sizes.  

UNS uses beveled 45 degree seams allowing a more clear and clean look while also providing more surface for strength.  They use Diamant Glass which gives a 91% clarity and beveled edges for a smooth awesome edge look.

All of the UNS Aquariums INCLUDE a tank mat which is needed for any glass or rimless aquarium to relieve stress points on the tank.