This paper presents our Context-aware Mobile Assistant Project (C-MAP). C-MAP is an attempt to build a personal mobile assistant that provides visitors touring exhibitions with information based on their locations and individual interests. We have prototyped the first version of the mobile assistant and used an open house exhibition held by our research laboratory as a testbed. The mobile assistant directs users with exhibition maps that are personalized based on the physical and mental contexts of the users. This paper also describes offsite services for overcoming temporal/spatial restrictions to facilitate communications and information sharing between exhibitors and visitors.