on the city of the museum you use the poke radar just up of the city a bunch of grass so you use there and you'll find larvitar
you can catch a larvitar on route 206 if dawns sister says you can.
swarm:route 206(40% chance)
In Pokemon platinum larvitar can be found in the north area of route 210 after obtaining the national pokedex, you have to use the poke radar to find one
I don't think you can. However, Larvitar can be caught in either Mt. Silver of Johto Safari Zone in HeartGold. Not sure which one though.
dawn's sister could tel you where it is tip: you need the national pokedex b zain abbasi: kinnn of platinum
After you beat the elite four and get your national poke'dex every day go to dawn's sister and in time she will tell you where to get a larvitar, catch a larvitar then evolve it into a pupitar then tyranitar.
Larvitar can be found in Mt.Silver.
to find larvitar go to the Seavault Canyon
No you cannot catch Larvitar in Pokémon Emerald.
catch a larvitar during a swarm on route 206 or using a poke radar on route 207 then evolve it at lv 30
Lots of Pokemon
mt.silver