Make an area with a 20 block gap in...

Make an area with a 20 block gap in between walls, this area is going to have 4 rooms, those rooms are going to be 10 x 10 in size with a 20 block height, the corridor is going to be about 50 blocks tall and have a entrance by stairs you will have to climb these stairs to leave the corridor, this build will have walld at least 3 blocks thick and will have an ender and cosmic theme, each room will have windows about 5 blocks wide 3 blocks high and 2 or 3 in depth of wall