The Mining Hill is used to enter the mines. Here the player travels downwards through levels, crushing ores with the Hammer that can be used for upgrading tools. As the you travel farther downward, the mines become more dangerous. Bring an escape rope (bought at the Mining Hut) so you can quickly leave the mines if necessary.
One cannot sleep in the Mining Hill. Similar to the Nether, a bed will explode. This can be very bad as it can damage the ladders you need to leave the mines. Torches will help you see, but will not stop mob spawns.