A Milano nasce il “muro della gentilezza”

Participio passato come aggettivo
Past particles as adjective

Appeso alla parete si può trovare di tutto
(Hanging on the wall, one can find everything)

In Italian, the past participle can be used as an adjective to describe the state, condition, or quality of a noun. When used as an adjective, the past participle agrees in gender (masculine or feminine) and number (singular or plural) with the noun it modifies.

In the sentence above, the past participle “appeso” is used as an adjective to describe the state or condition of various objects that can be found hanging on the wall.
The past participle “appeso” is derived from the verb “appendere” (to hang) and agrees in gender and number with the noun it refers to (“tutto”, masculine singular). 

Here are more examples:

• Chiusa la porta, mi sono sentito più al sicuro. (Having closed the door, I felt safer.)
  In this sentence, “chiusa” is the past participle of “chiudere” (to close).

• Rotto il vetro, abbiamo dovuto chiamare un tecnico per ripararlo. (With the glass broken, we had to call a technician to fix it.)
  In this example, “rotto” is the past participle of “rompere” (to break).

• Finita la doccia, sono andato a dormire. (After finishing the shower, I went to sleep)
  In this sentence, “finita” is the past participle of the verb “finire” (to finish).