Al-Ybi is a mostly unremarkable desert city in Klatch. Al-Ybi's reputation for boringness has entered it in folklore as the place where Klatchians invented the concept of zero. This makes sense to noted Ankh-Morporkian scholars, who reason that since empty desert is basically nothing, nothing is a ready natural resource to Klatchians.
Since nothing happens in Al-Ybi, it is also a safe place for criminals to claim to have been whenever they stand accused of a crime.
The only excitement in Al-Ybi occurred when the greedy Seriph of the city was cursed by a dyslexic deity so that everything he touched turned into "glod". Glod was a blameless dwarf in a far off mountain community who found herself being dragged to Al-Ybi and relentlessly duplicated. Over two thousand Glods later, the curse wore off. To this day, the people of Al-Ybi have a reputation for being both bad-tempered and short in stature.
Al-Ybi's name is a play on alibi, a person's claim to have been elsewhere when a crime has taken place. This fits with Fred Colon's assertion that Klatchians invented everything with al- in the name, including al-gebra, al-cohol, and al-stronomy.
The cursed Seriph of Al-Ybi is a twist on the myth of King Midas. Turning everything into gold is bad, but turning everything into a furious Dwarf is possibly even worse.