Please assume the elevation of airport to 2000ft ASL. Under what conditions ATC might mandate aircrafts to fly at lower altitudes? What might be approximate speed at this distance?
Here is a typical landing at Paris CDG with a slope of about 3° (5%).
Jeppesen IFR approach plate, source
Runway altitude is 318ft.
- You see the altitude is 3000ft from 10.2NM until a distance of 7.2NM.
- Then it follows a radio glideslope at 3° (5%).
- Speed entirely depends on aircraft performance. A large airliner may fly at 140kt (A320), but a small GA aircraft may fly at 70kt (Cessna 172).
In addition there are obstacles, and there is an indication on the plate:
MSA 2000ft within D22.0 PGS. It means the minimum altitude which can be selected by a pilot within a circle of 22NM radius around PGS navaid (located at the airport) is 2000ft. Below this altitude there are obstacles outside of the approach path.
But as commented by @Bianfable, ATC may vector aircraft to speed up the landing, or to separate them. Vectoring means asking them to follow ATC indications instead of using a published procedure. This is not limited to landing aircraft.
In this case the aircraft may be instructed to fly at an altitude below the published one, but above the minimum radar altitude indicated on the first page of the documentation linked, in this case it's also 2000 ft until about the outer marker (OM) where it's 1500ft.
Jeppesen minimum radar alitudes, source
Note your question is difficult to answer as it cannot be assumed the landing is done in straight line, or the initial altitude is 3000ft (other approaches exist at this airport with a value of 4000ft as you'll see if your look at the linked documentation).
It will vary for a specific airport and direction of landing, and neighboring obstacles. A landing in a mountainous area might be different.