The Hidden Temple Wall (was called "Mayan Wall" before R30) is a pinkish-brown building-block with a cross-like pattern on all 6 sides. This block can be crafted in your Crafting Menu (default key "Q") or at Crafting Tables (that still exist in worlds created before R22 on September 16th 2015), but only after the recipe has been unlocked upon buying it in the Store as a part of the "Mayan Pack" (as of R24 in November 2015). To craft 8 (blocks of) Hidden Temple Wallss, you'll need (as of R30 in April 2016):