The photo can be found in Anatomy of a Ship - The Type XX! U-Boat pg. 33 by Fritz Kohl & Eberhard Rossler (accents missing). It is of the bridge of U-3017 showing the speaking tubes in the recesses for the bridge watch. Alongside are U-2518(l) and U-2502(r) with U-3515, forward with U-2529 and U-3514 alongside.
The snorkel had 2 tubes, one for the air intake and the other for engine exhaust. The tubes are ~2x the periscope's dia. The snorkel was also positioned on the starboard side of the conning tower.
The tubes shown are the attack periscope nearest with the navigation periscope forward.
The opening with the curved side is the steering position.