Cetinje may indeed be littered with old-time reminders of its days as Montenegro's capital city, but just 4km away lies an attraction that makes the town look positively modern. Millions of years old, Lipa Cave is one of the country's largest caves – and the only one open for organised visits – with 2.5km of illuminated passages and halls filled with stalactites, stalagmites and freaky natural pillars. Tours take 60 minutes, including a road-train ride and short walk to the entrance.
Be sure to bring warm clothes, as temperatures hover around 10°C year-round.
If you'd like to delve deeper, call ahead to arrange a 2½-hour Cave Extreme tour (adult/child €50/25), which includes some abseiling.