Context : The optically invisible infrared-source NGC 2264 IRS 1 lying north of the Cone Nebula is thought to be a massive young stellar object ( \sim 10 M _ { \sun } ) .
Although strong infrared excess clearly shows that the central object is surrounded by large amounts of circumstellar material , no information about the spatial distribution of this circumstellar material has been available until now .

Aims : We used the ESO Very Large Telescope Interferometer to perform long-baseline interferometric observations of NGC 2264 IRS 1 in the mid-infrared regime .
Our observations resolve the circumstellar material around NGC 2264 IRS 1 , provide the first direct measurement of the angular size of the mid-infrared emission , and yield direct constraints on the spatial distribution of the dust .

Methods : We analyze the spectrally dispersed interferometric data taken with MIDI at two different position angles and baseline lengths .
We use different approaches ( a geometrical model , a temperature-gradient model , and radiative transfer models ) to jointly model the observed interferometric visibilities and the spectral energy distribution .

Results : The derived visibility values between \sim 0.02 and \sim 0.3 show that the mid-infrared emission is clearly resolved .
The characteristic size of the MIR-emission region is \sim 30 - 60 AU ; this value is typcial for other YSOs with similar or somewhat lower luminosities .
A comparison of the sizes for the two position angles shows a significant elongation of the dust distribution .
Simple spherical envelope models are therefore inconistent with the data .
The radiative transfer modeling of our data suggests that we observe a geometrically thin and optically thick circumstellar disk with a mass of about 0.1 M _ { \sun } .

Conclusions : Our modeling indicates that NGC 2264 IRS 1 is surrounded by a flat circumstellar disk that has properties similar to disks typically found around lower-mass young stellar objects .
This result supports the assumption that massive young stellar objects form via accretion from circumstellar disks .