  We report the detection of large hydrocarbon cycles toward several cold dense
clouds. We observed four sources (L1495B, Lupus-1A, L483, and L1527) in the Q
band (31-50 GHz) using the Yebes 40m radiotelescope. Using the line stack
technique, we find statistically significant evidence of benzonitrile
(C$_6$H$_5$CN) in L1495B, Lupus-1A, and L483 at levels of 31.8$\,\sigma$,
15.0$\,\sigma$, and 17.2$\,\sigma$, respectively, while there is no hint of
C$_6$H$_5$CN in the fourth source, L1527. The column densities derived are in
the range (1.7-3.8)$\,\times\,10^{11}$ cm$^{-2}$, which is somewhat below the
value derived toward the cold dense cloud TMC-1. When we simultaneously analyze
all the benzonitrile abundances derived toward cold clouds in this study and in
the literature, a clear trend emerges in that the higher the abundance of
HC$_7$N, the more abundant C$_6$H$_5$CN is. This indicates that aromatic cycles
are especially favored in those interstellar clouds where long carbon chains
are abundant, which suggests that the chemical processes that are responsible
for the formation of linear carbon chains are also behind the synthesis of
aromatic rings. We also searched for cycles other than benzonitrile, and found
evidence of indene (C$_9$H$_8$), cyclopentadiene (C$_5$H$_6$), and 1-cyano
cyclopentadiene (1-C$_5$H$_5$CN) at levels of 9.3$\,\sigma$, 7.5$\,\sigma$, and
8.4$\,\sigma$, respectively, toward L1495B, which shows the strongest signal
from C$_6$H$_5$CN. The relative abundances between the various cycles detected
in L1495B are consistent -- within a factor of three -- with those previously
found in TMC-1. It is therefore likely that not only C$_6$H$_5$CN but also
other large aromatic cycles are abundant in clouds rich in carbon chains.
