It may be small, but there can be few more dramatic frontiers in Australia. This shallow causeway, which is impassable when the tide's in, crosses the East Alligator River from Kakadu National Park on the west bank to Arnhem Land to the east. And watching you as you cross is the river's healthy and rather prolific population of saltwater crocs. Ask at Border Store or Jabiru's Northern Land Council for tide timings.
If you're not going across, wander down to the slightly elevated lookout on the west bank, but go no further as crocs lie in wait right by the riverbank. As recently as January 2017, a man was killed by a croc while trying to wade across.
If you're heading east into Arnhem Land, you'll need a permit, which you obtain from the Northern Land Council in Jabiru.