Translate the following question to SQL: Which three cities have the largest regional population?

Schema: CREATE TABLE city (
    City_ID INT   PRIMARY KEY,
    City TEXT,
    Hanzi TEXT,
    Hanyu_Pinyin TEXT,
    Regional_Population INT,
    GDP REAL,
    UNIQUE (City_ID)
);

CREATE TABLE match (
    Match_ID INT   PRIMARY KEY,
    Date TEXT,
    Venue TEXT,
    Score TEXT,
    Result TEXT,
    Competition TEXT,
    UNIQUE (Match_ID)
);

CREATE TABLE temperature (
    City_ID INT   PRIMARY KEY,
    Jan REAL,
    Feb REAL,
    Mar REAL,
    Apr REAL,
    Jun REAL,
    Jul REAL,
    Aug REAL,
    Sep REAL,
    Oct REAL,
    Nov REAL,
    Dec REAL,
    UNIQUE (City_ID),
    FOREIGN KEY (City_ID) REFERENCES city(City_ID)
);

CREATE TABLE hosting_city (
    Year INT   PRIMARY KEY,
    Match_ID INT,
    Host_City TEXT,
    UNIQUE (Year),
    FOREIGN KEY (Match_ID) REFERENCES match(Match_ID),
    FOREIGN KEY (Host_City) REFERENCES city(City_ID)
);
user
SELECT city FROM city ORDER BY regional_population DESC LIMIT 3
assistant