I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "Downtown San Diego is the central business district of San Diego, though the city is filled with business districts. These include Carmel Valley, Del Mar Heights, Mission Valley, Rancho Bernardo, Sorrento Mesa, and University City. Most of these districts are located in Northern San Diego and some within North County regions."? 

Where is Mission Valley?