It first appeared in the third season and made numerous appearances until the ninth. The architectural style changed in the later seasons. Although never mentioned by name in an episode, it was first named in an eighth season learning segment. It returned in Tale of the Brave in the same architectural style as the third season and later appeared in The Adventure Begins and has made infrequent appearances since.
- The lake next to the tunnel shrank in the later seasons, gradually being replaced with hills, until it was no longer visible. It became visible again in Tale of the Brave when it returned in CGI.
- The number of tracks leading through the tunnel changes between one to three tracks on many occasions. Since Tale of the Brave, there have been two tracks.
- The Castlelated Tunnel is a modified version of this tunnel.