Activate Thawing Glaciers by paying ({1} magic symbol) and tapping it, searching your library for a basic land card and putting it onto the battlefield tapped.
The land enters the battlefield, triggering Retreat to Coralhelm and Nissa.
Resolve the Nissa trigger, adding ({1} magic symbol) .
Resolve the Retreat to Coralhelm trigger, untapping Ley Druid.
Activate Ley Druid by tapping it, untapping Thawing Glaciers.
Repeat.
Results
Near-infinite landfall triggers.
Put all basic lands from your library onto the battlefield.