Context : For the past two decades , the three-dimensional structure of sunspots has been studied extensively .
A recent improvement in the Stokes inversion technique prompts us to revisit the depth-dependent properties of sunspots .

Aims : In the present work , we aim to investigate the global depth-dependent thermal , velocity , and magnetic properties of a sunspot , as well as the interconnection between various local properties .

Methods : We analysed high-quality Stokes profiles of the disk-centred , regular , leading sunspot of NOAA AR 10933 , acquired by the Solar Optical Telescope/Spectropolarimeter ( SOT/SP ) on board the Hinode spacecraft .
To obtain depth-dependent stratification of the physical parameters , we used the recently developed , spatially coupled version of the SPINOR inversion code .

Results : First , we study the azimuthally averaged physical parameters of the sunspot .
We find that the vertical temperature gradient in the lower- to mid-photosphere is at its weakest in the umbra , while it is considerably stronger in the penumbra , and stronger still in the spot ’ s surroundings .
The azimuthally averaged field becomes more horizontal with radial distance from the centre of the spot , but more vertical with height .
At continuum optical depth unity , the line-of-sight velocity shows an average upflow of \sim 300 ms ^ { -1 } in the inner penumbra and an average downflow of \sim 1300 ms ^ { -1 } in the outer penumbra .
The downflow continues outside the visible penumbral boundary .
The sunspot shows , at most , a moderate negative twist of < 5 ^ { \circ } at \log ( \tau ) = 0 , which increases with height .
The sunspot umbra and the spines of the penumbra show considerable similarity with regard to their physical properties , albeit with some quantitative differences ( weaker , somewhat more horizontal fields in spines , commensurate with their location being further away from the sunspot ’ s core ) .
The temperature shows a general anti-correlation with the field strength , with the exception of the heads of penumbral filaments , where a weak positive correlation is found .
The dependence of the physical parameters on each other over the full sunspot shows a qualitative similarity to that of a standard penumbral filament and its surrounding spines .

Conclusions : The large-scale variation in the physical parameters of a sunspot at various optical depths is presented .
Our results suggest that the spines in the penumbra are basically the outward extension of the umbra .
The spines and the penumbral filaments , together , are the basic elements that form a sunspot penumbra .