Entrance to the congress centre of the Vienna Hofburg (Austria 1973)

Stamp Entrance to the congress centre of the Vienna Hofburg it reflects the thematic directions:

Gates is the plural of gate, a point of entry to a space which is enclosed by walls. 

A building or edifice is a structure with a roof and walls standing more or less permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes and functions, and have been adapted throughout history for a wide number of factors, from building materials available, to weather conditions, to land prices, ground conditions, specific uses and aesthetic reasons. Buildings serve several needs of society – primarily as shelter from weather, security, living space, privacy, to store belongings, and to comfortably live and work. A building as a shelter represents a physical division of the human habitat (a place of comfort and safety) and the outside (a place that at times may be harsh and harmful).

Convention and exhibition centers are facilities you can use for large-scale events and conferences. It's used to gather groups or individuals with common interest in one convenient location. This is where you can share ideas and learn something new while strengthening your network and reaching out to a wider audience.

A conference is a meeting, often lasting a few days, which is organized on a particular subject, or to bring together people who have a common interest. Conferences can be used as a form of group decision-making, although discussion, not always decisions, is the primary purpose of conferences. The term derives from the word confer.