Catch Unown
Unown is the only Pokemon that has more than two different forms. It can take 28 different shapes, one for each letter of the alphabet and two forms of punctuation. Hidden Power is the only attack Unown can learn. Unown is the only Pokemon found in the caves of the Ruins of Alph and cannot be found anywhere else. Walk around inside the caves and you will randomly be brought into battle with an Unown.
Rock Smash
There are boulders all over the Ruins of Alph that can be broken with the Pokemon move Rock Smash. Each broken boulder could yield an item, such as a rare fossil. In "SoulSilver," the boulders could produce the Dome Fossil and Old Amber. These fossils can be revived into Pokemon at the Pewter Museum of Science. The Dome Fossil will become Kabuto and the Old Amber becomes Aerodactyl.
Catch Rare Pokemon
There is a small patch of grass in the Ruins of Alph that can be accessed from Union Cave. This area contains the Pokemon Natu and Smeargle. Natu is a psychic and flying-type Pokemon that evolves into in Xatu. Natu can be found on Route 28 and Mt. Silver as well, but only if you use the move Headbutt on trees. There is a much higher chance of finding Natu in the grass in the Ruins of Alph. Smeargle only knows the move Sketch. Sketch will permanently copy the last move of the Pokemon it is battling. Smeargle also appears in the Safari Zone, but at a substantially lower rate than in the Ruins of Alph.
Chamber Challenges
Each of the chambers in the ruins has its own challenge. Use an "Escape Rope" to beat the first chamber. Use the move Flash to get through the second chamber. In the third, face the wall that says "Water." Select a Water Stone in your inventory and select "Use." Ho-oh must be the first Pokemon in your party to open the fourth and final chamber.