The Place, in Northlands Pavement, Pitsea, has undergone a transformation, since work started in February.
The refurbishment saw a new foyer created and the cafe improved.
Free activities on the day, including pilates, karate, jujitsu, craft classes, and a bouncy castle, entertained youngsters.
Information was also provided to over-50s on which fitness classes they can get join.
Tory Terri Sargent, Basildon councillor responsible for the community, said: “This is a great opportunity to promote all our services, encourage new users and for our current users to increase their memberships.”