For nearly 2,000 years, a huge Roman structure lay hidden beneath Budapest. Now archaeologists have uncovered the remains but they’re still trying to work out exactly what it was built for.
Dating back to the 3rd or 4th century AD, the building stretches for hundreds of metres and ends in a mysterious polygonal tower. It appears to have been an important public building linked to the Roman military, but due to its thin walls it’s unlikely to be a fortress, and it doesn’t appear on any surviving maps.