This is an Easter Egg in the game.
The skeleton, which is hanging upside-down from the icy cave's ceiling also has a glowing, enchanted sword on the ground nearby. This is a reference to Star Wars, where Luke Skywalker set off a trap in a cave in Hoth causing him to drop his lightsaber and hang from the cave ceiling.
cave
the hanging gardens are a giant pillar of stone, hanging from the ceiling of a giant cave. The whereabouts of this cave are unknown.
its in one of the guards inventory
Well I know Septimus is in a little cave/hut thing north of College of Winterhold.
Near the skeleton of the dinasour above the cave men.
A stony spike hanging from the roof of a cave is a stalactite. Stalactites are formed by minerals deposited by dripping water in caves, creating the icicle-like formations that hang from the ceiling.
it means that skeletons have died or there is chests underneath
Stalactites are the formations hanging down from the ceiling of a cave due to mineral deposits dripping from the top.
Some bats are capable of hanging upside down from cave ceilings using their feet. This adaptation allows them to rest or sleep in caves without needing to hold on using energy. Hanging from cave ceilings also provides bats with a vantage point for spotting prey or avoiding predators.
Stalactites hang down from the ceilings of caves.
It is at the end of the Nordic ruin Volskygge. Volskygge is to the far West, past Drragon Bridge, just South of Lost Echo Cave.
The Skeleton Key is actually not an item as you would expect but a button of sorts. In the Sealed Cave of Final Fantasy III there's a dead end with skulls. One of these skulls is the actual key you need to interact with to proceed.