It is naturally hilly, but it has been flattened out quite a bit by artificial means, to make it easier to build houses and roads over. Many towns and cities still have many hills, some of considerable size.
hilly
Parts of Australia's deserts are flat and others are hilly.
Flat
flat
flat in the north (near the sea) to mountained in the south (part of the Alps)
the terrain of Haiti is hilly and isn't that flat
Flat
is golden sands hilly or flat
Extremely flat
relatively flat
Greece is mostly hills and mountains.
Belgium is flat