Our offices are ok, considering it's the poverty stricken third sector. Modern(ish) building, decent physical environment, good IT, good air con/heating (except in our office, which used to be a laboratory), very clean, unlimited free tea and coffee (including a bewildering array of fruit and herbal teas, real coffee and hot chocolate) and a proper kitchen with real ovens and hobs, so you can cook a lunch.
But it's the ethos/culture which makes it great. It's a very supportive environment, very caring, tolerant, easy going and scrupulously equal and accepting of all diversities. All our clients are vulnerable in some way (mostly mental health and learning disability, but also addictions and disability), and quite a few former clients are now staff. You can "buy" an extra week's leave, flexible working is positively encouraged, almost all managers are compassionate and supportive, and we have a good laugh. It doesn't feel hierarchical and staff feel supported, valued and respected.
It's also in the top 10 of family-friendly employers.
I've been happier there than anywhere else I've worked, which is why I've stayed nearly 13 years.