The historically most important building is the Esterházy manor-house (castle) which is located on the site of the once famous medieval water-castle of Sempte. The manor-house was built in 1840 in classicist style; it was later altered in empire style. It is now in ruins and awaits restoration. The remains of the medieval castle are hidden in its walls. The local authority and civil association “Vodný Hrad” do their best to save this symbol of the town.
John the Baptist Church is situated on the opposite place of the former parish church since 1781. When the former church burned down on 2 August 1777, the Esterhazy family decided to build a new one and they moved there the two renaissance tomb-stones with relief of anti-Turkish warriors.
The Holy Trinity-column can be seen left from the church. It was erected in the second half of the 18th century in baroque style with the sculptures of Saint Peter, Saint Paul and Saint Anne.
The old City Hall was built in 1909 by architect János Tomascheck, native of Sereď. There is a great council chamber in the building, which is now used as marriage room. It is decorated with valuable paintings depicting views of St. Petersburg brought by Nikolaus Esterházy from his diplomatic mission in 1771.
The Slovak Holocaust Museum will open in Sered in January 2016.