  We present observations of the center of the Galactic globular cluster NGC
6273, obtained with the HST/WFPC2 camera as part of the snapshot program
GO-7470. A B, V color-magnitude diagram (CMD) for ~28,000 stars is presented
and discussed. The most prominent feature of the CMD, identified for the first
time in this paper, is the extended horizontal branch blue tail (EBT) with a
clear double-peaked distribution and a significant gap. The EBT of NGC 6273 is
compared with the EBTs of seven other globular clusters for which we have a CMD
in the same photometric system. From this comparison we conclude that all the
globular clusters in our sample with an EBT show at least one gap along the HB,
which could have similar origins. A comparison with theoretical models suggests
that at least some of these gaps may be occuring at a particular value of the
stellar mass, common to a number of different clusters. From the CMD of NGC
6273 we obtain a distance modulus (m-M)_V=16.27+-0.20. We also estimate an
average reddening E(B-V)=0.47+-0.03, though the CMD is strongly affected by
differential reddening, with the relative reddening spanning a 0.2 magnitude
interval in E(B-V) in the WFPC2 field. A luminosity function for the evolved
stars in NGC 6273 is also presented and compared with the most recent
evolutionary models.
