From the publisher:

Subterranean Crossroads contains 25 six-by-six tiles that can be used to link together dozens of different tile sets from SkeletonKey’s library of products. This set adds flexibility and versatility by connecting different terrain types with the tiles listed below.

• Cave Passages/Ghoul Burrow
  
• Caves of Peril/Dungeons
  
• Caves of Peril/Ghoul Burrow
  
• Caves of Peril/Ghul's Labyrinth (Ptolus)
  
• Iron Dungeons/Caves (wide)
  
• Dungeons/Ice Caves/Sewer Chambers
  
• Dungeons of the Dead/Ghoul Burrow
  
• Dungeons of the Dead/Ghul's Labyrinth (Ptolus)
  
• Dungeons of the Dead/Iron Dungeons
  
• Dungeons of the Dead/Ptolus Sewers
  
• Dungeons (narrow)/Ice Cave Pools
  
• Flooded Caves/Ghould Burrow/Sewer Tunnels
  
• Flooded Caves/Ghul's Labyrinth (Ptolus)
  
• Flooded Caves/Ice Caves
  
• Ghoul Burrow/Ghul's Labyrinth (Ptolus)
  
• Ghoul Burrow/Ice Cave Pools
  
• Ghoul Burrow/Iron Dungeons
  
• Ghould Burrow/Ptolus Sewer
  
• Ghul's Labyrinth (Ptolus)/Iron Dungeons
  
• Ice Cave Pools/Iron Dungeons
  
• Iron Dungeons/Ptolus Sewers
  
• Wooden Bridge/Flooded Caves/Dungeons
  
• Wooden Bridge/Flooded Caves/Cave Passages
  
• Wooden Bridge/Flooded Caves/Ghul's Labyrinth (Ptolus)
  
• Wooden Bridge/Flooded Caves/Dungeons of the Dead
  
• Wooden Bridge/Flooded Caves/Ice Caves
  
• Wooden Bridge/Flooded Caves/Iron Dungeons