Avengers Set Pictures Need Your Expert Eyes

Can you decipher what the mystery item is in these spy pictures from Cleveland, midst all the burning rivers, rust belt recession and Avengers filming? Depending on what you think it is, you could also suppose the pictures are spoilers.

Superhero Hype attained them from a spy of theirs, and made guesses that it might be some kind of alien spaceship. Not a bad guess, obviously. Do you recognise it from any Avengers back issues?

Rich adds: Did a Skrull steal an Asgardian space ship?