Which preposition to use with caracas

on Occurrences 5%

To the Senate of the United States: I transmit to the Senate, for its consideration with a view to ratification, a treaty of amity, commerce, and navigation, and for the surrender of fugitive criminals, between the United States and the Republic of Venezuela, signed at Caracas on the 27th of August last.

in Occurrences 3%

He returned to Caracas in company with Emparan, appointed captain-general of Venezuela by the central junta at Seville.

Which preposition to use with  caracas