。
There was broken glass on top of the fence.
Literal
Fence's above [on-には] broken glass [subject-が] existed.
塀 is 'fence/wall' (an exterior wall or enclosure, distinct from 壁 which is a building wall). 割れたガラス is 'broken glass' — a relative clause where 割れた (broke/cracked) modifies ガラス. This detail evokes a security measure common on walls in some countries.