This race is taking place at a super cool spot matching Halloween vibes: a 2,5-kilometre-long tunnel system in Kőbánya. On 4 November, you can complete several distances (including categories for school children and younger), even in a costume, if you feel like that. Some magic and spookiness are on the cards, but there is no need to be scared – it's a family-friendly event after all.
 
More details here (Hungarian-only), but you can message the organisers here as well.