Darksteel Garrison

Fortified land has indestructible.
Whenever fortified land becomes tapped, target creature gets +1/+1 until end of turn.
Fortify {3} ({3}: Attach to target land you control. Fortify only as a sorcery. This card enters unattached and stays on the battlefield if the land leaves.)

The List

Future Sight

Fortified land is indestructible.
Whenever fortified land becomes tapped, target creature gets +1/+1 until end of turn.
Fortify {3} ({3}: Attach to target land you control. Fortify only as a sorcery. This card comes into play unattached and stays in play if the land leaves play.)

Fortification is to lands what Equipment is to creatures. Except for the difference regarding what kind of permanent it can affect, Fortifications and Equipment follow the same rules.

If Darksteel Garrison and the fortified land would be destroyed at the same time, only Darksteel Garrison is destroyed.

The second ability triggers whenever the fortified land becomes tapped, not just when it’s tapped for mana.

The triggered ability is mandatory. If you don’t have a creature to target, you must target another player’s creature, if possible.