Local Stargate

Taking a new route home on Friday at dusk, I entered an unknown precinct. It was deserted apart from a series of mysterious rings, such as this below. I didn't have time to explore further but there are a few explanations.

1. This is the One Ring. It didn't in fact fall into Mount Doom with Gollum.

2. It's a Stargate. If I jump through I'll find myself on the set of a cheesy science fiction series with Richard Dean Anderson.

3. Some workmen have played a prank, and have propped up some cabling.