The space is filled with falling sand that drifts down forever and never piles. Its whole extent is 2,834 km across.
A mouth opens on the river delta near Yirostylg where licensed guides from a closed caste control access to the gate. The light goes out for 11 days in every year while people prepare for darkness.

The whole world leans toward one direction, and the seam is common where gates open as well here as anywhere.
from Annals of the Frozen Delta, by Draestorn
Cargo passes free while a drone meets every arrival carrying a weapon.
from Factors' Account Books of the River Trade, by Zekimi
A mouth opens on the river delta near Yirostylg. Licensed guides from a closed caste control access to the gate.
Forests are owned like mines because timber floats and sells well. The world owes more through the gate than it can pay.
The regent rules in exile while the rightful ruler lives off-world. Yirostylg is a river delta whose channels change course every few years.