Developed as an island city. Alexander the Great connected it to the mainland by a causeway during his siege (332BC). "The present-day city of Tyre covers a large part of the original island and has expanded onto and covers most of the causeway, which had increased greatly in width over the centuries because of extensive silt depositions on either side" (Wiki)

"The ancient part of the town is situated on a peninsula (previously an island) connected to the mainland by a narrow man-made isthmus" (Wiki)

A thousand years ago Lulea district consisted of an archipelago where the sea level was ten metres higher than today. The church hill of present-day Gammelstad was a small island at the mouth of the Lule river. (Wiki)

Dubrovnik and Ragusa used to be separate settlements the second being located on an island. The two were united in the 12th Century when the channel which separated the two was filled with earth.

Barsa-Kelmes, a former island in the Aral Sea: "as the sea became more shallow it steadily grew, until in the 1990s it ceased to be an island" (wiki)
See en.wikipedia.org

Schokland is a former island in the Dutch Zuiderzee. Schokland lost its status as an island when the Noordoostpolder was reclaimed from the sea in 1942.

The Ile des Cygnes - not to be confused with the still existing Ile aux Cygnes - was an island in the Seine, between Invalides and the Champ de Mars. The channel between the island and the river bank was filled in in 1812, during the construction of the pont d'Iéna. The Musée du quai Branly is located on the site of the former island. (wiki)
See en.wikipedia.org

The Plaza de la Constitucion area of Mexico City was originally built in 1325 on a the southern part of an island in Lake Texcoco as "Tenochtitlan" by the Tenochca people. The northern part of this island contained the settlement of Tlatelolco, having previously been settled by another Nahuatl group the Tlatelolca - its remains are centred on the "Plaza of the 3 cultures". For many years the lake (whose Aztec controlling dams had been destroyed during the Conquest) was capable of flooding the centre of the city. Drainage was "improved" over the centuries but the problem was not "finally" solved until the 1960s with the building of deep tunnels to take water out of the Texcoco basin -at the cost of aridity/sinking land etc.

Kazimierz used to be an island until 1880.

Includes the former Penon island
See www.casbahdalger.dz