The apartment is a 10-minute walk from the Brussels-north train station, making access from Brussels-Zaventem airport easy and inexpensive (~$10 one way). The apartment is located at one end of the pedestrian area of central Brussels, directly across from the Hotel Plaza. The location is a walk up, with on-street entrances, adjacent to McDonald's. The room was clean, stocked with plates and dishes, a refrigerator and working kitchen. A grocery store is less than two minutes walk away, making it easy to use this apartment for some meals, since dining out in Brussels in extremely expensive.
The room itself faced the street, and the curtains did little to block the light. Windows are not well insulated, and noise is an issue. If you have any trouble sleeping, a blackout mask and earphones (ear plugs are not enough) are a must. The furnishings are good, but starting to show their age. The photo used in the Expedia advertisement is not truly representative of the apartment in which I stayed.
Other commenters have written that this is in a terrible part of Brussels above a sex shop and that they saw people selling their bodies. It is near a sex shop that also sells lingerie, but those can be found on nearly every block in Brussels. I personally did not witness anyone participating in prostitution, and I did not ever feel unsafe in any way.
The apartment is also near the Brussels Metro, making travel throughout the city extremely easy and inexpensive.