  To obtain an unbiased sample of bright LyA blobs [L(LyA) > 10^43 ergs/s], we
have undertaken a blind, wide-field, narrow-band imaging survey in the NOAO
Deep Wide Field Survey Bootes field with the Steward Bok-2.3m telescope. After
searching over 4.82 sq. degrees at z=2.3, we discover four LyA blobs with
L(LyA) = 1.6-5.3 x 10^43 ergs/s, isophotal areas of 28-57 sq. arcsec, and broad
LyA line profiles (FWHM = 900-1250 km/s). In contrast with the extended Lyman
alpha halos associated with high-z radio galaxies, none of our four blobs are
radio-loud. The X-ray luminosities and optical spectra of these blobs are
diverse. Two blobs (3 and 4) are X-ray-detected with L_X(2-7 keV) = 2-4 x 10^44
ergs/s and have broad optical emission lines (C IV) characteristic of AGN,
implying that 50% of our sample blobs are associated with strong AGN. The other
50% of blobs (1 and 2) are not X-ray or optically-detected as AGN down to
similar limits. The number density of the four blobs is ~3 x 10^{-6} Mpc^{-3},
comparable to that of galaxy clusters at similar redshifts and 3x lower than
that found in the SSA22 proto-cluster at z=3.1, even after accounting for the
over-density of that region. The two X-ray undetected blobs are separated by
only 70" (550 kpc) and have almost identical redshifts (< 360 kpc along the
line-of-sight), suggesting that they are part of the same system. Given the
rarity of the blobs and our discovery of a close pair, we speculate that blobs
occupy the highest density regions and thus may be precursors of today's rich
cluster galaxies.

Astrophysics