Car Insurance

The rental car company will provide it. You can get third party insurance via you own car insurance, special policies, perhaps credit cards, etc. The problem with third party insurance is that it becomes a triangle of pointed fingers should something bad happen.

European countries are pretty tough on liability insurance company requirements, and the rental company will have it on all their cars.

Where they charge you is on collision damage waivers (CDW) and their newest racket, personal property coverage if someone breaks into the car.

Many of those in North America with comp. and collision insurance are also covered on rental cars in Europe. And many credit cards cover collision insurance on a secondary basis on cars paid for on the credit card. Check with your insurance company to see what your policy covers.

Last time, I used my Costco Amex card's CDW program. For a flat $25 dollar fee, it covered CDW for the entire rental (about 20 days in my case). There are limits and exclusions about which states can offer this and which countries you can use it in. You have sign your card up in advance (I had the wrong Amex card and opened a new one) and make sure you're billed when you rent the car (supposed to be automatic, but I had to call to have them manually charge me). It's a good enough deal that it's worth looking into.

https://www.americanexpress.com/us/content/card-benefits/car-rental-insurance.html

See more tips about the CDW: http://www.ricksteves.com/travel-tips/transportation/car-rental-cdw.