The bank account in question is called a 'rental-deposit account', or in German, a 'Mietzins-Kautions-Konto' available at any bank. Usually the landlord opens the account at a bank, and sends you the contract for signature. The money is paid to the landlord, who will transfer it to this special account. Within 20 days you will receive a confirmation from the bank, that your money has been deposited. A yearly statement is sent to you, where the interest is also credite. In Switzerland, the maximum allowed for deposits is 3 monthly rents. An alternative to deposit money in deposit account, is to make an insurance instead at a yearly fee.