The Skopje Aqueduct stands about 5 kilometres north of the city centre, just off the road toward Kumanovo. It is an impressive structure: 386 metres long and up to 12 metres high, with 55 arches still standing. Its origins have been debated — it may be Ottoman rather than Roman — but regardless of its exact date, the aqueduct is an unexpectedly grand piece of ancient infrastructure in an industrial suburb.
Getting there requires a taxi or a bus toward the northern suburbs; it is not walkable from the centre. But it is worth the effort for the sheer scale of the thing. There are no facilities, no entrance fee, and often no other visitors. You can walk along the base of the arches and examine the construction closely.