Robert G.
Yelp
The Foundacao Calouste Gulbenkian is "probably" Lisbon's major art museum. There is no other museum with a name like "Museo de Arte de Lisboa," so this must be it.
I've known about the Gulbenkian for years and, in all the times I've been to Lisbon, I've only been there once. I'm glad I went. The only other museum I've been to is the National Coach Museum (incredibly detailed horse-drawn carriages) and that was impressive, but that was a long time ago. Lisbon has no shortage of museums, though some are more niche-like in their focus.
The reason many people may not see the Gulbenkian is because most of Lisbon's touristic highlights are in its natural amphitheater-like bowl near the harborfront square and the hills immediately flanking it. The Gulbenkian is above the the city's "amphitheater" and a bit north of the famed Marques de Pombal rotunda.
Calouste Gulbenkian was a successful Armenian business magnate who bestowed his art collection upon the city of Lisbon. The art includes that of some of the European masters and, as such, is primarily European, Middle Eastern, and Asian in its focus. Mostly, the works are paintings, sculptures, and ceramics. However, they are rounded out by displays of apparel and furnishings, the latter of which are especially ornate. You would wonder why anyone would even want to use them or sit on them. As such, they're better off here ... in this museum.
Your Metro exit is Praca de Espanha, which is near the city's bullring and near the bus queuing area that can take folks to the south shore and the lengthy strand of beaches by crossing the Ponte 25 de Abril. With such an efficient Metro system, there is no reason not to go slightly north in the city, away from the more touristic highlights, and see the Gulbenkian Museum. There are also gardens, an indoor-outdoor cafe', and, of course, special exhibits which are often extra cost venues.
I was going to say the Gulbenkian is a 4 star situation. However, when one considers that there's a free day each week, that the main admission ticket is reasonably priced to begin with, and that the Lisboa Card brings the admission down to about 5 Euros, the Fundacao Calouste Gulbenkian museum is as good as it gets.