The Congress secretariat has pre-booked a number of hotel rooms in Tallinn. Rooms with special prices can be booked alongside with registration to the Congress. If you contact the hotels directly, the special prices do not apply.
To ensure that you have a room at the hotel at the preferred rate, it is imperative that you book your room as early as possible. There are several other events taking place in Tallinn during the same period, so you may have to pay a higher rate and/or stay in another location.