Context : We have started a campaign to identify massive star clusters inside bright molecular bubbles towards the Galactic Center .
The CN15/16/17 molecular complex is the first example of our study .
The region is characterized by the presence of two young clusters , DB10 and DB11 , visible in the near infrared , an ultra-compact H ii region identified in the radio , several young stellar objects visible in the mid infrared , a bright diffuse nebulosity at 8 \umu m coming from PAHs and sub-mm continuum emission revealing the presence of cold dust .

Aims : Given its position on the sky ( l = 0 \aas@@fstack { \circ } 58 , b = -0 \aas@@fstack { \circ } 85 ) and its kinematic distance of ~ { } 7.5 kpc , the region was thought to be a very massive site of star formation in proximity of the Central Molecular Zone .
One of the two identified clusters , DB11 , was estimated to be as massive as \sim 10 ^ { 4 } M _ { \sun } .
However the region ’ s properties were known only through photometry and its kinematic distance was very uncertain given its location at the tangential point .
We aimed at better characterizing the region and assess whether it could be a site of massive star formation located close to the Galactic Center .

Methods : We have obtained NTT/SofI deep JHK _ { \mathrm { S } } photometry and long slit K band spectroscopy of the brightest members .
We have additionally collected data in the radio , sub-mm and mid infrared , resulting in a quite different picture of the region .

Results : We have confirmed the presence of massive early B type stars and have derived a spectro-photometric distance of \sim 1.2 kpc , much smaller than the estimated kinematic distance .
Adopting this distance we obtain clusters masses of M _ { \mathrm { DB 10 } } \approx 170 M _ { \sun } and M _ { \mathrm { DB 11 } } \approx 275 M _ { \sun } .
This is consistent with the absence of any O star , confirmed by the excitation/ionization status of the nebula .
No He i diffuse emission is detected in our spectroscopic observations at 2.113 \umu m , which would be expected if the region was hosting more massive stars .
Radio continuum measurements are also consistent with the region hosting at most early B stars .

Conclusions :