The Wall

The city was surrounded by a wall. In the distant past, whatever architects built the city had ensured there was plenty of room to expand, with the wall erected far from the center. They probably believed there was so much space that they'd never run out. Or that the city would die before it grew so large as to matter.

But here we were teeming like a coffee cup, the only thing holding the place together an invisible tension that might burst at any moment.

No one knew what, if anything, existed beyond the wall. Only that it was dangerous.

For the prompt Frontier