Ultima VII has quite possibly the most fully-featured debugging tool ever, and you don't need to download an external program or even modify the game in any way to access it. All you need to do is start the game with the command line paramater "abcd<ALT-255>" (where <ALT-255> is a special character created by holding ALT and pressing 255 on the numeric keypad. It looks like a blank space, but isn't.)
This video shows off the debug mode, as well as some of the more interesting hidden elements in Ultima VII.
Ultima VI has a similar debug menu as well, though it's not quite as impressive as this one...
There is also a third hidden entrance to the cheat zone, located just outside the Gargoyles' house in Britain.
Set a chest at the foot of the tree and step onto it and you'll be there.
And for a complete overview of the teleporters in the cheat room, check this link.