Ideal Land is explicitly a building used to gain new buffs. It has a garden where you place Ornaments; collecting and placing more Ornaments yields more buffs, and upgrading the building also grants buffs. Available at Keep 12. Note: the Triumphal Arch cannot exceed Lv5 unless Ideal Land is Lv7+. All menus stay usable during upgrade. Building-level buffs (Lv1-10): Construction Speed +2% -> +47%; All Troops HP, Attack, Defense each +5% (Lv2) -> +45% (Lv10). Leveling the building requires Prosperity Points, gained only by PLACING ornaments (not merely owning them); required points scale 500 (Lv2) to 26,000 (Lv10), each level also needing Keep 12 plus escalating resources. Ornament types: Basic (no buffs/points -- skip), Gem-purchasable (points only; placing all = 450 points for 460,000 gems), Limited (both buffs AND points). Limited ornaments come mainly from the Voyage to Civilizations event via Golden Commemorative Coins/Ladders (coins don't expire). RED Champion limited ornaments give large buffs (e.g. Notre-Dame de Paris: March Size +5000, enemy Ground/Mounted HP -10%, attacking Ranged Attack +15%). Garden expandable with gems (32x32 for 50k gems at Lv3; 40x40 for 100k gems at Lv5). For a bot: the Construction Speed and All-Troops buffs make Ideal Land a worthwhile base_dev target where free Limited ornaments are available.
Original research source: Evony Guide Wiki