Acropolis was a site of bustling human activity with many Byzantine, Frankish, and Ottoman structures. The dominant feature during the Ottoman period was a mosque inside the Parthenon, complete with a minaret. The Acropolis was besieged thrice during the Greek War of Independence (two sieges from the Greeks in 1821–1822 and one from the Ottomans in 1826–1827. A new bulwark named after Odysseas Androutsos was built by the Greeks between 1822 and 1825 to protect the recently rediscovered Klepsydra spring which became the sole fresh water supply of the fortress. After independence, most features that dated from the Byzantine, Frankish, and Ottoman periods were cleared from the site in an attempt to restore the monument to its original form, "cleansed" of all later additions. German neoclassicist architect Leo von Klenze was responsible for the restoration of the Acropolis in the 19th century, according to German historian Wolf Seidl, as described in his book Bavarians in Greece. Second World War At the beginning of the Axis occupation of Greece in 1941, German soldiers raised the Nazi German War Flag over the Acropolis. It would be taken down by Manolis Glezos and Apostolos Santas in one of the first acts of resistance. In 1944 Greek Prime Minister Georgios Papandreou arrived on the Acropolis to celebrate liberation from the Nazis. Archaeological remains The entrance to the Acropolis was a monumental gateway termed the Propylaea. To the south of the entrance is the tiny Temple of Athena Nike. At the centre of the Acropolis is the Parthenon or Temple of Athena Parthenos (Athena the Virgin). East of the entrance and north of the Parthenon is the temple known as the Erechtheum. South of the platform that forms the top of the Acropolis there are also the remains of the ancient, though often remodelled, Theatre of Dionysus. A few hundred metres away, there is the now partially reconstructed Odeon of Herodes Atticus. All the valuable ancient artifacts are situated in the Acropolis Museum, which resides on the southern slope of the same rock, 280 metres from the Parthenon. Site plan Site plan of the Acropolis at Athens showing the major archaeological remains. Parthenon Old Temple of Athena Erechtheum Statue of Athena Promachos Propylaea Temple of Athena Nike Eleusinion Sanctuary of Artemis Brauronia or Brauroneion Chalkotheke Pandroseion Arrephorion Altar of Athena Sanctuary of Zeus Polieus Sanctuary of Pandion Odeon of Herodes Atticus Stoa of Eumenes Sanctuary