Much of the answer will depend on how you define multisensory. Are you most interested in areas of the brain where multiple primary sensory streams converge together to form secondary representations, or are you interested in areas of the brain that simply have access to that kind of information?
I will throw in for consideration one of my favorite multisensory brain areas: the insula. It is the primary sensory cortex for gustatory and interoceptive sensory information (Craig et al., 2000) and seems to play an important role in temporal coincidence of crossmodal stimuli (Calvert, 2001). This includes tactile-auditory association (Renier et al., 2009), tactile-visual association (Gentile et al., 2010), auditory-visual association (Bushara et al., 2001) to name a few.
With regard to the example in your question, De Araujo et al. (2003) found that the anterior orbitofrontal cortex was one of the few regions that didn't respond to taste, didn't respond to smell, but did respond when taste and smell were simultaneously presented. Orbitofrontal cortex might be my second favorite multisensory brain area...
- Bushara KO, Grafman J, Hallett M. (2001) Neural Correlates of Auditory–Visual Stimulus Onset Asynchrony Detection. Journal of Neuroscience, 21(1), 300-304.
- Calvert GA. (2001) Crossmodal Processing in the Human Brain: Insights from Functional Neuroimaging Studies. Cerebral Cortex, 11(12), 1110-1123.
- Craig AD, Chen K, Bandy D, and Reiman EM. (2000) Thermosensory activation of insular cortex. Nature Neuroscience, 3(2), 184-190.
- De Araujo IET, Rolls ET, Kringlebach ML, McGlone F, and Phillips N. (2009) Taste-olfactory convergence, and the representation of the pleasantness of flavour, in the human brain. European Journal of Neuroscience, 18(7), 2059-2068.
- Gentile G, Petkova VI, and Ehrsson HH. (2010) Integration of Visual and Tactile Signals From the Hand in the Human Brain: An fMRI Study. Journal of Neurophysiology, 105(2), 910-922.
- Renier LA, Anurova I, De Volder AG, Carlson S, VanMeter J, Rauschecker JP. (2009) Multisensory Integration of Sounds and Vibrotactile Stimuli in Processing Streams for “What” and “Where”. Journal of Neuroscience, 29(35), 10950-10960.