cities = {
    "Tehran": {
        "population": 8500000,
        "area": 730,
        "province": "Tehran"
    },
    "Mashhad": {
        "population": 3200000,
        "area": 431,
        "province": "Khorasan Razavi"
    },
    "Isfahan": {
        "population": 2000000,
        "area": 5520,
        "province": "Isfahan"
    }
}

print(cities["Tehran"]["population"]) # 8500000
print(cities["Mashhad"]["province"]) # "Khorasan Razavi"