Lisbon is the name of a city, a proper noun which should be capitalized.
There is no English adjective for a person or thing of or from Lisbon, but the proper adjective in Portuguese is Lisboeta.
Kentuckian is the proper adjective for Kentucky.
Someone from Israel is called an "Israeli".
The proper adjective for George is Georgian.
The proper adjective for Siam is Siamese.
The proper adjective for Antigua is Antiganantigan
The noun Lisbon is a proper noun, the name of a specific place.A proper noun is always capitalized.
Kentuckian is the proper adjective for Kentucky.
The proper adjective for southwest is "southwestern."
The proper adjective is Haitian.
The proper adjective for Portuguese is "Portuguese."
Someone from Israel is called an "Israeli".
The region where Lisbon is is called Great Lisbon, or in portuguese, Grande Lisboa.
Vietnamese is the proper adjective for Vietnam.
Lisbon has one Airport, called Aeroporto da Portela, but is also known as the Airport of Lisbon.
No, old is not a proper adjective. A proper adjective is an adjective derived from a proper noun, such as Swiss cheese, Bolivian pottery, Chinese silk, etc.
The proper adjective for George is Georgian.
The proper adjective for Siam is Siamese.