Best dog for a calm household

People assume Great Danes need enormous amounts of exercise. Mine is perfectly satisfied with two moderate walks a day. He is calm, dignified, and surprisingly quiet in the house. He follows me from room to room, parks himself with a thud on the floor near me, and sighs contentedly. He greets visitors with a friendly wag of his enormous tail. He is the most low-key dog I have owned despite being the largest.