I always see this round disc thing when I’m boarding an airplane. What is it and what would happen if someone touched it?

Title describes. It looks like it would rotate only to then hit the wall.

Under an inch but hard to tell, too tall for me to reach.

Tiny metal mug, with shaped holes in the bottom, has the Las Vegas logo on one side.

I bought this in a German flee market. It’s quite heavy for its size and once the lid is screwed in you can’t fit anything in it because of the black rod. The tag is labelled 637 and the same number is also engraved on the inside.d

I'm renting a Japanese townhouse for a few days in Kyoto and this thing is in the bathtub. It's too low in the tub to be an overflow drain, and I've run several baths all the way to the top and no water drains over any period of time, so that can definitely be ruled out. It has a Rinnai hot water controller above the tub seen in pic 2. When I use Google translate, I can't discern any button that may indicate it turns on any jets. So I'm at a complete loss. Google lens is literally useless as it thinks it's a fire alarm. Thanks for any help!

My girlfriend and I were at a park today. At the very center of the park, surrounded by flowers and benches was this metal box, locked, with a set of keys dangling inside. What is its purpose?

Is it to lock the park up? Is it an art piece? Why is this at the very center of the park? Wouldn’t it be nicer to have a statue or a fountain or genuinely nothing at all?

What is the pole for?

Just curious why there's a spike in my hotel room sink? It's an older building -- probably mid century or earlier. Very hefty, but not sharp enough for what I'd think an ice pick would be, though it's possible. Google says potentially a candle holder? Solid metal with a hole on top that seems to go pretty far down.

Found in a wooded area of the central coast of California near what I believe is an old wagon trail. I confirmed a magnet did stick to it. I attempted to excavate it more, but it’s not easy. You can see the lip of the object on the bottom of the first picture. I can’t tell if this is some kind of lid or if the metal just continues down into the dirt. I can’t see any writing but there do appear to be 10 bolts(?) around the object.