Leave Managua along main highway NIC-4. After about 16 km, turn right on NN-222 to enter Parque Nacional Volcán Masaya. Google will draw you in a bit early on what is clearly a more challenging spur of the NN-222. You’re on the right route if you pass the museum after just about a kilometer on your way up. From here it’s about 5 km to the summit where there is a parking area and a walking trail around the desolate crater of Volcán Santiago and the lusher crater of Masaya. Camping is permitted on the museum grounds which will probably mean it’s just you and the night security guard.
Leaving the national park the next morning, it’s another 25 km along the NIC-4 to Granada where a variety of accommodations and beautiful, historic downtown district awaits.