If Sugriva’s order to search the southern areas was a description of the Malaya Archipelago, then Ravana’s Kingdom would have been in Southeast Asia. Sita was found in Lanka’s capital Lankapuri, meaning Island City by the vinara Hanumān. The description of the Island City is interesting:
Right in the heart of the city, Hanumān saw in the main square numerous spies of Rāvaṇa; and these spies looked like holy men, with matted hair, or with shaven heads, clad in the hides of cows or in nothing at all. In their hands they carried all sorts of weapons, right from a few blades of grass to maces and sticks. They were of different shapes and sizes and of different appearance and complexions. Hanumān also saw the garrison with a hundred thousand soldiers right in front of the inner apartments of Rāvaṇa.
Hanumān approached the palace of Rāvaṇa himself. This was a truly heavenly abode. Within the compound of the palace and around the building there were numerous horses, chariots, and also aeroplanes. The palace was built of solid and pure gold and the inside was decorated with many precious stones, fragrant with incense and sandalwood which had been sprinkled everywhere: Hanumān entered the palace.- Vālmīki (1)Swami Venkatesananda (1988) The Concise Rāmāyaṇa of Vālmīki, Sundara 4, Book 5, Canto 6, Page 231
Most aspects of the description seem appropriate to an ancient city: the city walls, the mansions, the music and bards, and the horses and the chariots. However, the aeroplanes do seem out of place. The Sanskrit word is vimāna (विमान) which was translated as aerial-car before aeroplanes were invented in the 1900s. After the invention of aeroplanes, vimāna has become the modern word for aircraft or aeroplane in several Indian languages including Hindi. The term vimāna is not found in the surviving versions of the Ṛigveda, in which the gods flew around on flying-chariots, however vimāna are also found in the Mahābhārata, and later Hindu texts. The following is the definition of the word vimāna from the 1899 Monier-Williams Sanskrit-English dictionary:

A Comparison of the Worlds Largest Aircraft: the Hindenburg, a Mil V-12 Helicopter, an Antonov An-225, and an Airbus A380
The word aeroplane did not exist in 1899 when Sir Monier Monier-Williams published A Sanskrit-English Dictionary: Etymologically and Philologically Arranged with Special Reference to Cognate Indo-European languages, therefore he could not have used the term aeroplane. Moreover, a seven-story aeroplane is still science-fiction today, as the largest passenger aeroplanes currently in the sky are the two-story high Airbus A380s first flown a decade ago.(3)Philip Kaplan (2005) Big Wings The largest cargo plane in the sky is the Antonov An-225 Мрiя (Dream),(4)Military Factory (August 23, 2012) Antonov An-225 Mriya (Cossack) Heavy Lift Strategic Long-Range Transport which could theoretically be retro-fitted to be a three-story aircraft, and would still be dwarfed by a seven story aircraft. A seven-story aircraft would be the size of a Zeppelin, of which the largest, the Hindenburg, was only designed to carry around 100 people including the crew.(5)Ernst Lehmann (1937) Zeppelin: The Story of Lighter-than-air Craft The British Imperial Airships of the period were also designed to carry only 100 passengers or 200 troops on three decks. It could be another century or two before seven-story aircraft are being flown in the skies above Earth.
References
1. | ⇑ | Swami Venkatesananda (1988) The Concise Rāmāyaṇa of Vālmīki, Sundara 4, Book 5, Canto 6, Page 231 |
2. | ⇑ | Monier Monier-Williams (1899) A Sanskrit-English Dictionary: Etymologically and Philologically Arranged with Special Reference to Cognate Indo-European languages |
3. | ⇑ | Philip Kaplan (2005) Big Wings |
4. | ⇑ | Military Factory (August 23, 2012) Antonov An-225 Mriya (Cossack) Heavy Lift Strategic Long-Range Transport |
5. | ⇑ | Ernst Lehmann (1937) Zeppelin: The Story of Lighter-than-air Craft |