In the early days of Q3 there was a CTF mod released called Alliance. This was, and still is, a highly professional mod that adds a lot of interesting game play focused features to CTF matches.
This release contains 28 levels. All of which can be played with or without the Alliance mod. The maps were made around 2001 and may look a little basic compared to more recent releases, but don't be fooled by the visuals - game play is king and should be the only judge for these old maps.
If you have a small home or office LAN, maybe you play with a few friends online, then grab these maps and give them a go.
There is also a second Alliance map pack released that contains another 13 maps.
Note: A re-packed version of the Alliance mod (version 3.3) is available. It is about 59MB and well worth the download. The re-pack cleans up a few things and merges version 3.0 of Alliance with the 3.3 patch release.