Lighting Hanukkah Candles on a High Floor

I live on a high floor in a residential building and light candles at the window, which is 12 meters above the street. What should I do?

If the candles are placed above twenty cubits, the obligation is not fulfilled, and these twenty cubits are measured from the street level [public domain]. [The measure of twenty cubits is 11.54 meters, and some say 9.60 meters]. There is no difference whether you light at the entrance of the house or at the window; it must be within twenty cubits from the street floor. However, in your case, where there is no other option because there is no place in the apartment to light, and the custom is to light at the window to fulfill Rashi's opinion that lighting at the entrance of a residential building does not fulfill the obligation, it is advisable to place flashing colored lights [such as those used to decorate a sukkah] next to the candles in a way that attracts the attention of passersby in the public domain to look up above twenty cubits, and then it can be said that you fulfill the obligation [similar to the case of a decorated beam that is effective regarding an eruv ('amlatra'), even if the beam is placed above twenty cubits, because it attracts the attention of passersby in the alley]. Combined with the fact that the buildings opposite see this, or if there is no other choice, light at home in the presence of household members. There is uncertainty in all these measurements - whether to measure the height of the candles from the flame, from the candles, or from the menorah. The rabbis are divided on this, and in practice, we hold the main opinion that the measurement is from the place of the flame.

Shulchan Aruch (Orach Chaim, Siman 671, Section 6); Mishnah Berurah (Subsection 28); Eruvin (3:); Shulchan Aruch (Orach Chaim, Siman 363, Subsection 26); Azmera Leshimcha Bulletin (Issue 118).