ノリもさる事ながら、会場と一体化したような快感が忘れられない。

、。

Setting aside how good the vibe was, I can't forget the rush of feeling at one with the venue.

Literal

Vibe [also-も] leave-aside [while-ながら], venue [with-と] unified-did [like-ような] pleasure [subj-が] cannot-forget.

~もさることながら is a formal set phrase meaning 'not only X (which itself goes without saying), but especially Y' — with さる from the classical 然る 'that sort of' and ながら 'while / though.' 一体化する 'to become unified with' uses the productive ~化 suffix that builds change-of-state verbs from nouns (一体 'one body' + 化 '-ification'). ~ような 'like / as if' is the full prenominal form of the ~みたい class. 忘れられない is the potential negative of 忘れる ('cannot forget').