The N70 provides a "long way round" access from Tralee to the N71 at Kenmare, via the County Kerry Coast. The majority of the route, along with the northern end of the N71 and western end of the N72 makes up the Ring of Kerry tourist route.
The N70 starts on the southern section of the Tralee bypass, at a triple point with the N21 and N22. At the next roundabout, it rejoins its original route and climbs uphill away from the town, passing through Castlemaine where it bridges the River Maine at its most downstream crossing-point. From here it continues southwestward, crossing the River Laune to enter Killorglin, where the N72 comes in having crossed the length of County Cork. The road now follows the south shore of Castlemaine Harbour, though the estuary generally stays out of view.
At Cahersiveen the road turns to run south and takes a more inland route to Waterville, where the road slides through the short gap between Ballinskelligs Bay and Lough Currane. It crosses the River Currane and then winds its way round the mountainous area of this part of the county, still staying near the coast, up to Blackwater Bridge. From here, it's a straighter run into Kenmare, where the road ends on the N71.
The N70 originally started at a junction with the N21 and N69 on Castle Street in the centre of Tralee. The numbering around Tralee changed when the bypass opened in 2013.