Why many Italian towns are built on hills?

I’ve recently visited Italy and I noticed that many Italian towns are built on hills and not in valleys. A typical Italian town is built on a hill and the church is usually on the top of the hill. I’ve seen there many towns like that. In most countries the towns are usually built in valleys. I wonder why is it like that in Italy?

Most of the hill towns date back to the Middle Ages. At that time, building on a hill made the town more defensible, especially if it was surrounded by a wall, which most were. Italy was governed (if you can call it that) by many warring factions at the time, so security from attack was a big deal.