A rusty tram clatters past us. An uninterrupted line of cars slowly moves along Leó Frankel Street. Businessmen in dark suits hurry to their desks. Women in high heels walk carefully on the cobbled pavement. Between the houses, the ferries on the Danube can be seen, drifting past the Isle of Margaret that divides the town. We are in the middle of the Budapest morning rush hour. Our team attracts attention from passersby. We are carrying a van load of diving bottles and boxes through a narrow iron gate. The stone wall next to the cave is soon covered by diving equipment.