Here was a mighty wall built to keep the sojourners out. It fell flat. God had bigger plans.

Joshua 6:20

The walls of Jerico

So the people shouted when the priests blew the trumpets. And it happened when the people heard the sound of the trumpet, and the people shouted with a great shout, that the wall fell down flat. Then the people went up into the city, every man straight before him, and they took the city.
Bible Gateway link: Joshua 6:20 (NKJV)