The people of the town of San Rafael del Rio could find themselves split between Spain and Catalonia if the region ever secedes.
The border between Catalonia and the neighbouring region of Valencia cuts right through the community whose 500 residents fear the conflict between Catalan and Madrid authorities will literally split the town in two.
Guadalupe Espinosa, a 47-year-old psychologist who lives on the Catalan side of the river, said: "People are nervous and scared because they feel this is a free-fall.
"I don't like armies or borders, but maybe we will have one here. Who knows?"
Catalan leaders have said they will declare independence for the northeastern region after a weekend referendum that Spain declared illegal and tried to stop by force.
That could have particular implications for San Rafael, where the border cutting through the town until now has been a mere curiosity.
Spain's constitutional court has ordered a temporary halt to a special session of Catalonia's parliament next week where regional officials are expected to vote on breaking away from Spain.
The opposition Socialist bloc in the regional parliament, where separatist parties have a narrow majority of seats, had called for Monday's session to be blocked.
Lawyers for the regional parliament had also warned that the session would be illegal because it discusses results of a referendum over the weekend that had been previously suspended by the constitutional court.
Sunday's independence referendum has sparked a major political crisis in Spain.
Spain's prime minister, meanwhile, urged the separatist leader of the regional Catalan government to cancel plans for declaring independence to avoid "greater evils".
In an interview with Spain's EFE news agency, Mariano Rajoy said the solution in Catalonia "is the prompt return to legality and the affirmation, as early as possible, that there will be no unilateral declaration of independence, because that way greater evils will be avoided".
Catalan leader Carles Puigdemont has indicated the region will formally declare independence.