I don't know if it was already discussed here, but I didn't found it anywhere. The view distance in The Elder Scrolls: Arena is controlled by the green Detail bar in the game. The game does not allow you to enlarge the green bar beyond the limits of the Detail yellow box, but you can do it this way:

* Download the UNP utility for DOS from http://unp.bencastricum.nl/
* Extract the UNP.EXE file from the unp411.zip archive into the Arena directory.
* In the Arena directory, execute this command: unp a.exe
* Launch some hex editor.
* If you have the floppy disk version 1.06 of Arena, go to the 0x40235 hex offset. If you have the CD-ROM version 1.07 of Arena, go to the 0x40687 hex offset.
* Arena's Detail bar is set to 0A hex for new games. When a new game is started or a savegame file is loaded, the Detail bar can be changed to a new view distance between 00 and 2D hex. Using a hex editor, you can change this value between 00 and FF hex, so it can be several times bigger. Of course, FF is for fast DOS computers or emulators.
* Save the modified a.exe file.

If you change the view distance value to more than 2D hex in a hex editor, the green Detail bar in the game will be larger than its yellow box, so it will look strange, but everything else will be OK. When you save your game, the view distance value is saved to your savegame file. But if you change the green Detail bar in the game, then you cannot change it beyond the limits of its yellow box. So if you want to continue the game with the increased view distance, don't touch the green Detail bar. This is a problem which I don't like, but unfortunately I wasn't able to find the offset in the savegame file, where the distance value is stored. So if you touch the green Detail bar and then save your game, you will not be able to increase it again beyond the 2D hex value in your savegame file.

If anyone would be able to find the view distance value in the Arena savegame file, it would be much better and simpler solution with the possibility to change the value any time.