When we took the stable tour after seeing a Spanish Riding School performance in Vienna, we noticed the stallions resting in their stalls. One was completely flat out, dead to the world, oblivious to the group passing right by his stall.
These were not large stalls, and he was sleeping diagonally to maximize the available space. To give an idea of the close quarters, my husband could’ve touched the stall fronts on each side while standing in the middle of the aisle.