District of Columbia is about 402 times bigger than Holy See (Vatican City).

Holy See (Vatican City) is approximately 0 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 40,127% larger than Holy See (Vatican City). Meanwhile, the population of Holy See (Vatican City) is ~1,000 people (600,723 more people live in District of Columbia).
Tip: This to-scale comparison of Holy See (Vatican City) vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.