Usually crystal clear, Sheffield's famous water fountains in the Peace Gardens turned an unusual shade of green.Â
Thankfully, there's no need to worry about pollution as the fountains were actually turned green for the Out of This World festival.Â
Sheffield has already had its fair share of alien activity this month with Dr Who arriving in the city.Â
But there were more monsters, aliens, ghouls and superheroes than usual as the festival returned for a fifth year.
Thousands of sci-fi, comic book, gaming and magic fans came to the city to see the weird and wonderful sights on offer.
Spread across the city centre, the free event was once again divided into three zones based on the themes of sci-fi, magic and Halloween.
Simon Houghton tweeted: 'Glad the rain held off for #outofthisworld cool stuff and turned the water fountain spooky green. #Sheffield'