"Level one, Minister for Magic and Support Staff."
--disembodied witch's voice (DH12)
The top floor of the Ministry of Magic’s headquarters. This level is the location of the offices of the Minister for Magic and other administrative staff (DH12, 13).
In disguise Harry and Hermione take the lift up to this level when they infiltrate the Ministry. Hermione has to go back down to the lower levels, but Harry uses his invisibility cloak and prowls around in search of the locket Umbridge got from Mundungus. He finally finds Umbridge's office, enters after setting of a decoy detonator, and goes over the room thoroughly. Although he does not find the locket, he learns a lot about what the Ministry is up to and he recovers Moody's magical eye (DH12, DH13).
Arriving at Level One, the lift opens onto a corridor that extends on both sides. The corridor has thick purple carpeting and is lined with well-polished wooden office doors each displaying a small plaque proclaiming the name and position of the individual inside. In stark contrast to the bustle of lower levels, it is calm and extremely quiet (DH13).
During Thickness's time in office, Level One seems to be mostly devoted to the persecution of Muggle-borns, and an open area outside of Dolores Umbridge's office is filled with twelve desks and used as a workplace for the assemblage of propaganda pamphlets (DH13).
As senior undersecretary to the minister, Umbridge attaches Alastor Moody's magical eye to her shiny mahogany door. The interior of her office much resembles that she had at Hogwarts, with dried flowers and images of kittens, but now also contains filing cabinets filled with intel on enemies to the regime (DH13).
Once, a poisonous duck from Experimental Charms on one of the lower levels made its way to Level One (DH13).