From Alla (
http://ffxi.allakhazam.com/db/bestiary.html?fmob=1813) (and found VERY fast using Google I might add...):
The Altepa Gate
You need to get this gate open before you can reach the NM. The gate is located at (I-6) of Western Altepa but is only accessible through Quicksand Caves and can only be opened when 4 columns/switches are activated. At this point, you're going to have to split up the alliance into 4 seperate groups to go after each column/switch to open the gate. Remember, mobs in Quicksand caves will still aggro at 70+ so it's a good idea if everybody can Sneak themselves.
1) Emerald Column
Send 2 party members to (D-12) of Western Altepa. From there, have them zone into Quicksand Caves and head for (F-7) on the map. On the way, they may encounted a door that can only be opened by having 2 people stand on a weight-switch. Once at (F-7) they will find a sand whirlpool where they can drop through to a lower level. Once they've dropped, have them head to the zone at (H-4) on the map. Once they are back in Western Altepa, they should see the Emerald Column. Have them click on the column and head back to join the rest of the alliance.
2) Sapphire Column
Send another 2 party members to (G-5) of Western Altepa. Have them zone into Quicksand Caves and pass through another weight-switch doorway and head for the zone at (D-8 ) on their map. Once there, have them look for the Sapphire Column and examine it to activate it. After they are done, have them catch up with the rest of the alliance.
3) Topaz Column
Send the rest of the alliance to (J-9) of Western Altepa and have them wait at this spot until the gate is opened. Send 1 party member into Quicksand Caves and have them head for (D-11). Then have them head to the farthest room on their right-hand side and fall through a whirlpool to a lower level. From there, have them zone to (C-6) to Western Altepa where they can reach and examine the Topaz Column. When they are done, have them re-join the alliance at (J-9).
4) Ruby Column
Once the other 3 switches/columns have been activated, gather the entire alliance at (J-9) of Western Altepa and enter Quicksand Caves. Head north to (K-6) and drop through yet another whirlpool. From there, have the entire alliance zone to (N-4) on the map to Western Altepa.
From here, send 1 person to activate the Ruby Column while the rest of the alliance heads north through the interconnected tunnels to the Altepa Gate at (I-6). The Altepa Gate looks like a tall set of double doors. Once all 4 columns have been activated, the Altepa Gate will open and stay open for about 15-30 mins. Make sure everybody hurries through the gate and once the alliance is gathered behind it, proceed into Quicksand Caves.