Mausoleum of Origins

The Mausoleum of Origins can be found by talking to the archaeologist in the first structure in Fuchsia City. 8 badges are required to access. There will be a trainer battle as the archaeologist used to be a Gym Leader. After you have beaten him, you will be teleported to the area once you are ready and interact with him again. Many new Pokémon can be found in this area and the texture of grass has been changed to a more realistic kind.

Meloetta
You can get to battle and catch Meloetta by collecting a total of four 'Musical Notes' scattered around the Mausoleum of Origins. Once you have collected all four, go into the house with instruments and talk to the NPC. ''It is recommended that you save before talking to them as this is a ONE-TIME battle. ''He will then play a song using the music notes you have collected and then Meloetta will appear.

Zekrom and Reshiram
Zekrom and Reshiram can be found in the Mausoleum. For Zekrom, you must have Kyurem and an -type Pokémon in your Party. For Reshiram, you must have Kyurem as well and a -type Pokémon in your Party. Please note that Zekrom has a higher encounter rate than Reshiram.

The Mausoleum
The Mausoleum is a large temple built near the end of the area. You will encounter some lost trainers and a maze. Legendary Pokémon are also roaming in the grass patches and so are some Generation V Pokémon.