The summer house was built by Kilián Ignác Dientzenhofer between 1716 and 1721 for himself and his family. The marble Reiner Room, one of the jewels of the high civil Baroque in the Czech Republic, is decorated with frescos with mythological motifs of the Bacchus festivities by Václav Vavřinec Reiner. The summer house also included a Baroque French garden. After Dientzenhofer’s death, the house was acquired by František Ferdinand Buquoy, who modified the garden in Rococo style. Two side wings were added to the house probably around the end of the 18th century. In 1815 the building was purchased by entrepreneurs Mojžíš and Leopold Porges from Portheim, who built a factory to produce calico on half of the garden. In connection with the construction of the Church of St Wenceslas, other parts of the garden were parcelled and the house’s southern wing was demolished. The summer house was nationalised in 1945. In the 1950s the wall was demolished and the garden was modified roughly to its current form and made accessible to the public. When line B of the Prague metro was being built in the 1980s there was a construction site on the garden grounds. Later the roads were resurfaced and rows of horse chestnuts were planted as well as individual trees.
In the 1960s the exhibition gallery “D” was established here. This letter was a reference to the name of the house’s builder and original owner, Kilián Ignác Dientzenhofer. Since then it has also been a protected site. Portheimka is now the property of the Capital City of Prague and under the administration of the Prague 5 Municipal District. In 1992 the building was rented and renovated according to a design by architect Tomáš Zetek. Today the summer house consists of the former central part, a connecting corridor and the northern wing. The building’s multiform composition has been preserved; only the original entrance was relocated. On the ground floor in the space of the former Salla Terrena there is now a café – during the last reconstruction a well was discovered here dating from the 18th century. The gallery also operates successfully.