One of the more impressive and enduring LEGO sets for adults (well, ages 16+, anyway) is the LEGO Ideas Tree House. It's a massive three-unit tree house you can build with either green leaves or yellow leaves for an autumnal feel. It normally rings in at $250, but it's on sale for $75 off for Prime Day. Grab it before it's gone.

The 2,314-piece R2-D2 display model was officially retired by Lego in January, so this set was already hard to find.

A popular replica Animal Crossing set is now 38% off ahead of Prime Day. For art lovers, the Art Hokusai piece is finally on sale at 15% off. The problem with shopping Lego during Prime Day is that these items often sell out,