Address: Callas House, H-1061 Budapest, Andrássy Avenue 20.
https://goo.gl/maps/KYQgwCdz2Fn
The airport bus 100E stops in front of the exit of both terminals. The bus runs between the airport and Deák Ferenc tér and also stops at Kálvin tér and Astoria. You have to take the bus to Deák Ferenc tér, where you change to metro line M1 and get off the metro at the stop ‘Opera’. You’ll find the Callas House on the right side of the Opera House. The running time of the bus between Deák Ferenc tér and the airport is officially 40-60 minutes. A single ticket to the bus 100E costs 900 HUF (3 EUR).