Monoliths - definitely not aliens!
A few weeks back a monolith was discovered, in the desert in the state of Utah in the USA. Since then they’ve been popping up in various places around the world. The famous monolith from Kubrick’s 2001 A Space Odyssey (based on Arthur C. Clarke’s novels) would appear to be the inspiration for these.
It appears that the original in Utah was installed back in 2016, but remained undiscovered. Wikipedia has a list of all the monoliths discovered so far.
In this age of viral videos and publicity stunts, it’s easy to imagine that there’s a company behind this using it for some marketing purpose, though given how long it’s taken for the original to be revealed, that does seem unlikely.
While these monoliths have allusions to that in 2001, if it were aliens, they’d do something much more impressive. Simultaneously making them appear all over the world, for instance. Appearing levitating above the ground? Let your imagination run wild!
There is a serious side to this though, particularly the original Utah one. As has been pointed out, this is essentially littering on public lands. Such “artwork” attracts visitors to locations not prepared for a public onslaught, thereby endangering both the land and people’s lives who might decide to visit, ill-prepared for the journey.