Between 23 June and 2 December 1940, Lisbon realized the Exposição do Mundo Português (Portuguese World Exposition), that included an urbanization plan that encompassed the area of Belém, that included the Praça do Império.[1] The sculptures of the seahorses, that dominate the site, were completed by sculptor António Duarte were installed in 1940.[1]
A project to construct the Palácio do Ultramar (Overseas Palace) was initiated in 1952, situated on the eastern edge of the park, authored by architects Cristino da Silva and Jacques Carlu.[1]
In 1973, a commemorative monument to the poet Augusto Gil (1873-1929) was installed on the site, that included a bronze medallion and inscription by the municipal council of Lisbon.[1]
The rectangular 175 by 175 metres (574 ft × 574 ft) square consists of successive quadrangles, that structure the space into passages and greenspaces.[1] These converge in the central illuminated fountain on a square platform, covering an area of 3,300 square metres (36,000 sq ft).[1] On the extreme edges of the southern part of the square, along the Avenida da Índia are hippocamp statues (seahorses), over reflecting pools.[1]
"A acção da Câmara Municipal de Lisboa na Exposição do Mundo Português", Revista Municipal (in European Portuguese), Lisbon, Portugal, 1940, pp. 24–26{{citation}}: CS1 maint: location missing publisher (link)
"A fonte luminosa da Praça do Império, Nova maravilha de Lisboa", Revista Municipal (in European Portuguese), Lisbon, Portugal, 1963, pp. 31–33{{citation}}: CS1 maint: location missing publisher (link)
Acciaiuoli, Margarida (1998), Exposições do Estado Novo, 1934 -1940 (in European Portuguese), Livros Horizonte
Ferreira, Rafael Laborde; Vieria, Victor Manuel Lopes (1985), Estatuária de Lisboa (in European Portuguese), Lisbon, Portugal: Amigos do Livro, Lda.
Nobre, Pedro Nunes (2010), Belém e a Exposição do Mundo Português: Cidade, Urbanidade e Património Urbano, Projeto de mestrado em Património Urbano da Universidade Nova de Lisboa (in European Portuguese), Lisbon, Portugal: Universidade Nova de Lisboa