The Basement BBS was originally online from 1986 through 1998. The BBS was run on an Atari 800XL. On July 4, 2017, the Basement BBS returned online via telnet. The version that you can now telnet to was pieced together with backup floppy disks from 1990 through 1993.
The BBS includes restored messages/message bases from 1990 through 1993, some restored file sections, 21 online games, and lots of customization.
For best results, log in with an Atari 8-bit or a telnet client that supports ATASCII (Atari Mode). One such client is Syncterm. Syncterm is available for Windows, Linux, Mac OS/X, etc.
You can download Syncterm here.
The Basement's telnet address is: basementbbs.ddns.net port 9000.
If you rather not use a telnet client, then you can log in using a web client available at: http://www.sfhqbbs.org/telnet-basement.php.