Alma 31:13

for they had a place built up in the centre of their synagogue, a place of standing, which was high above the head; and the top thereof would only admit one person.

They had built a place in the center of their synagogue. It was a place for standing that was high above everyone’s head. The top of it only had room for one person.

In the center of each synagogue stood a tall platform—so high you had to look up to see the top. And the platform was only big enough for one person at a time.