Spectacular. Off road track that can be made with a Roadster. Better in july to september.
I like entering into the desert by north.
From Carcastillo take the NA-534. The road goes slightly up and some where before the top of the slope, turn right. Theres a sign indecating Bardenas Reales Enter. Its a track through 40 km.
Only one road possible. Cant get lost.
Places to visit around:
OLITE, the Castle ( touristic place, quite expensive)
You can sleep in TUDELA, NH HOTEL, have diner on the main city place.