The Interspace Border Gate is a travel checkpoint where city roads leave the stable Nullhaven signal and enter routes through open void space.
Layout
The gate contains three inspection lanes, a return corridor, a signal-visa reader, and a printed route board. Beyond the last barrier, ordinary city clocks stop agreeing with one another.
Crossing procedure
Travelers present a passport, declare restricted items, and wait for the route signal to match their destination stamp. The barrier opens only after the printed and electronic records agree.
Closures
The gate closes during strong black-sun activity and when an outward road is observed returning to the city from the wrong direction. Emergency return lanes remain open whenever a safe memory signal can be maintained.