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.

If you prefer building with no agenda, the Classic Creative Brick Box is down to just $15.29 this Prime Day. That's its best price ever. It includes 484 pieces, including bricks, windows, eyes, tires, wheel rims, and more, in 35 different colors, so you can build pretty much anything you can think up.

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