urbe is a synonym for City.
It is a population agglomeration where a series of social, commercial, cultural, administrative, educational exchanges occur, among others, located in a certain geographic space.
Urbe is a Latin word and comes from the radical urbs, the same as we find in all words related to the concept of the city, such as urban, urbanized, suburb.
In Portuguese, urbe is a singular feminine noun.
The plural of urbe is urbes.
In Latin urbe is a declension of the ablative case of the root urbs. And the city would correspond to what in the Portuguese language would be an adverbial adjunct to place.
The Latin variation urbi is the declension of the dative case, which can indicate direction, destination and reference, complementing verbs and nouns.
Urbi also represents what is related to the city, but it is also related to Rome. It would be like a maximum representation of what would be an urbi.
The word urbi is part of a Latin expression used by the Pope of the Catholic Church, in his Easter and Christmas blessing, "Urbi et Orbi", and means "to the city of Rome and to the world".
Learn more about meaning of the expression "Urbi et Orbi" .