tower, turret
樓 centers on a tall, multi-story structure: a tower or turret, often built for observation or defense.
樓 combines 木 (wood) with 婁, which likely contributes the sound and may relate to a multi-tiered structure. The character originally referred to a wooden tower or watchtower.
The left side 木 suggests a wooden structure, and the right side 婁 looks like a stacked, multi-level shape. Imagine a tall wooden tower with several floors, like a turret.
For ロウ, picture a row of wooden towers lined up: row -> ロウ, and each tower is a tall turret.