Your hand: Village, Distant Lands, Watchtower, 2 Coppers.
Play Village, drawing Crossroads.
Play Crossroads, reveal Distant Lands, draw Throne Room.
Throning a Watchtower is useless. Thanks to deck tracking, you know that there are 3 treasures and a key Action left in your deck before the shuffle. Thanks to last turn's Pearl Diver, you know that the bottom card of your deck is a Smithy (you didn't topdeck it last turn because the Pearl Diver had already drawn a Smithy and you only had 1 action left).
Now, if you TR the Distant Lands, then play Watchtower, you can draw the Treasures and the Smithy, play the Smithy, and continue your turn with 1 action remaining.
EDIT: This doesn't work; you could play the Distant Lands first, then the TR vacuously on the Watchtower.