World 3-4 (Super Mario Bros.: The Lost Levels) - Super Mario Wiki, the Mario encyclopedia
I present to you my Super Mario World Iceberg! Full Video Explanation coming soon. : r/IcebergCharts
I made a stage based on the secret levels from Super Mario Sunshine (code: 2RQ5D3RM) : r/SmashBrosStages
Super Mario Bros.: The Lost Levels World 3-4 Solution Map for Famicom Disk System by StarFighters76 - GameFAQs
The Secret Levels of Super Mario Bros.
Every Secret Exit in New Super Mario Bros. U (All 12) - Guide & Walkthrough
Official Lost Levels of Super Mario 3
Super Mario Bros POWER UP Card Game 3-8 Players Ages 8+
9 Intense Video Game Secret Levels You Can't Handle – Page 9
Are There More Secret Levels To Super Mario Brothers? - Super Mario Bros./Duck Hunt
Super Mario Bros. - Wikipedia