An Ineffective Pump
This old sump pump was doing nothing to keep the water out of the basement. If you notice, there's also no perimeter system in place so there's no way for the water to get to it in the first place.
Rusty Vent
This vent rusted from the high amount of humidity and water in the basement. It's definitely a sign that something's wrong!
Water Damage
You can see water pooling on the floor and how it's caused damage to the floor. It is also causing that wood to rot, and this creates potential for mold.