-----------------------The ancient city of Jericho was built, abandoned and rebuilt several times over many centuries. It was finally abandoned abut 1500 BCE at the time a severe eathquake damaged its outer walls, and not rebuilt until long after the establisment of the kingdoms of Israel and Judah. At the time attributed to Joshua and the military conquest of Canaan, there was, at most, a mud-brick village on the site of the former city, but no defensive walls.
One of the most famous episodes in the biblical conquest of Canaan was the assault on the city of Jericho. Joshua had the priests march around the city walls and Yahweh caused the walls to collapse, allowing the Hebrews to storm the city.
Now the city of Jericho was built upon a large mound of earth surrounded by an embankment with a stone retaining wall at its base. On top of this 12-15 foot high retaining wall was another mudbrick wall that was 6 foot thick and about 25 feet tall. Also, at the crest of this embankment was another similarly sized wall whose base was about 45 feet above the ground level outside the retaining wall. So if you were standing in front of the retaining wall, it would appear to you that the wall was over 70 feet tall.