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tokens: moderately warm ( T dust ≈ 50 K). With these conditions, the low-lying H 2 O lines at submm wavelengths (240 − 400 μ m) are efficiently pumped, but little absorption is produced in the far-IR with only significant absorption in the H 2 O lines at 75 and 108 μ m. Nevertheless, the inferred colums are more than enough to extinguish any line emission at short wavelengths, and indeed the Pa- α emission within r = 0.5 kpc primarily probes the western (near) side of the nuclear bar, with a morphology different from that of the continuum submm emission (Fig. 17 b). It is within the envelope region where the CO 2–1 line becomes very broad (Fig. 15 c), which is probably a direct consequence of the shocks produced by the inflowing gas and may be evidence of disordered motions that would eventually lead to a pseudobulge. High-lying molecular absorption lines in the far-IR are produced when the columns are so high that the far-IR continuum becomes optically thick ( González-Alfonso et al. 2015 ), and these conditions are also linked to the emission in the H 2 O448 line. In ESO 320-G030, a nuclear disk with projected radius of ≈40 pc attains these conditions, though still with moderately warm dust ( T dust ≈ 55 K). The disk is distorted, elongated in the direction of the bar, and highly turbulent (Δ V / V rot ≈ 1); it is thus expected to be geometrically thick (e.g., Cazzoli et al. 2020 ). At the center of the disk, an unresolved, extremely buried ( τ 100 ≫ 1) and very warm ( T dust ∼ 100 K for the far-IR photosphere; see González-Alfonso Sakamoto 2019 ) core component is identified from the absorption detected in very high-lying lines of H 2 O, of which the H 2 O 7 07 − 6 16 line at 71.95 μ m ( E lower = 640 K) is an excellent tracer. We estimate a core radius of R = 9 − 16 pc, but higher angular resolution observations are required to better determine its size. HCN vibrational emission has been recently detected in ESO 320-G030 (Falstad et al., in prep.), additionally indicating the presence of a very warm optically thick region. In such environments, trapping of IR radiation raises T dust and the mid-IR radiation density within the cocoon of dust, but the resulting SED does not show any enhanced mid-IR emission as only the photosphere is probed at mid- and even far-IR wavelengths ( González-Alfonso Sakamoto 2019 ). Because of their extreme extinction, the nature of these very compact nuclear components has been long debated; even X-rays and mid-IR high ionization tracers from a putative AGN are expected to be severely attenuated. ESO 320-G030 is undetected with the Swift /BAT all-sky survey observations 1 in the 14 − 195 keV band with a sensitivity of 8.4 × 10 −12 erg s −1 cm −2 , which translates into a luminosity of 6 × 10 8 L ⊙ . Assuming a ∼5% contribution to the bolometric AGN luminosity in the quoted band, the upper limit for L AGN is ≲10 10 L ⊙ ; however, absorption at 30 keV is still relevant for N H ∼ 10 25 cm −2 , and an AGN with ∼10% of the