does anyone know if there is a place where i can find hard monsters besides memoria?

The appropriately named Vile Island (a large island with amountain in the middle, located between the Outer and Forgotten Continents (not far from the Iifa Tree actually), is a good place to get a ton of EXP and AP. It's also a great place for having your party annhilated. The only enemies that inhabit the place, are Vans.

Despite their cute, lamb-like appearence, THEY WILL HURT YOU. They make mincemeat of your party, by nuking them with Meteor (often several times in a row, or blow a character out of the battle with Sneeze), so I wouldn't reccomend facing them until you're at a very high level. (You can't reach it without the Invincible or a Gold Chocobo either I'm afraid, as there is no grass to be found on the island, so the Hilda Garde 3 can't land there).

For an area for level building with a more moderate challenge, try the ledge above Gizmaluke's Grotto (which you can reach either by airship, a decent level chocobo or ladder from the Grotto underground). The only enemy that inhabits this ledge is the Grand Dragon. Although a pretty tough enemy early in the game, after a few rounds with them, they're quite easy (it's good for raising Freya's 'Dragon Crest' ability too), however, make sure you equip yourself with immunity against lightning, as it'll make battles against them much easier.

The plateau outside of Daguerreo is also good for this, as Grand Dragons live there too (as well as the occasional wimpy Gimme Cat.).

Actually, they're called Yans.

And you'll occasionally run into real easy monsters and Worm Hydras above Gizamaluke's Grotto.

But yeah, those are the best places to go.

the ledge infront of the grotto is decent because of the grand dragons, possible 8800 pnts a peice, good way to kill em is take quina and use lvl 5 death.

Well, there aren't really any other places to level up, other than those already mentioned. However, I do not recommend fighting the Yans until you are a decent level anyway. They will hurt you with Meteor, or use a very annoying attack called Sneeze, which will blow a member of your party away. Just pummel them with physical attacks and strong magic attacks, keep your HP levels high and you will emerge victorious.

If you are at a very low level and are right at the start of the game (the first time you visit Lindblum), get Zidane on his own and head to Hunters Gate. Outside are two forests that contain Bombs. They can be tricky, but will reward you with 178EXP each, which is a fairly high amount at that stage of the game. :)

Happy Killing
Muppet

You could go around the world and go to little forests and there you usually will find all the fights you need.

Outside of Daguerreo was always my favorite spot to level up. At least until you get up to a certain level, then it becomes to easy.

For a harder challenge, go to the island that Enkidoh was talking about, and fight with YANS. (Not Vans)

Those were the only two places I really cared to level up that, so good luck.

If my memory serves me, you could fight around on the Mist Continent during Disk 4. There's a place a little bit aways from the Chocobo Forest (the place is past the bridge) and you can fight Mistodons, Malboros, and the easy Ladybugs... Prinarily, you want a battle with 2 Mistodons. They give like 12000 EXP. each. Plus the Mistodons are easy to beat. I leveled up there for awhile but then I moved to the Grand Dragon place cause I couldn't stand fighting those Ladybugs anymore, they're too easy and gradually came up almost every tiem for me...

A great way to level up ONE player is to kill off the other 3 or make the other 3 get Virus (from Malboros and Chimeras) so they can still fight but not get EXP.