So Biden hasn´t left DC? Could he leave?

For non-us-anons, how big is DC? Is it the whole city, or just part of it, like city of London? DC includes Capitol, WH… what else?

…or is he really the president? Before noon oaths in inauguration? If not, would that make Trump still the president?? …and therefor possible to impeach?

Just things flying through my head.