Smyrna was destroyed in 600BC but Alexandria the great commissioned it to be rebuilt (which was done around 290BC). The new city that rose from the ashes of the old was much greater in magnificence than the first and has lasted to the present day as the city of Izmir. It is, in fact, the only city that Jesus spoke to in the book of Revelation that still exists today in the same location.
I am sure it is no coincidence that Jesus says to the persecuted church in Smyrna that he is the one who died and came to life. He came into the world to die our “second death” for us, taking on himself all our sin and shame and bearing in his body on the cross God’s anger at all our lies and lust and greed and murder. In his perfectly sinless body he satisfied God’s justice and rose again to make a way for us through to eternal life.
We now, by faith in Jesus, can go through the first death with no fear of the second. In the gospel, Jesus’ hand reaches out through death to take hold of ours. You may be hurt by the first but you will by no means be hurt by the second.
Rev 20:6 Blessed and holy is the one who shares in the first resurrection! Over such the second death has no power (ESV)
The Christians in Smyrna were sowing their lives in weakness but they would be raised in power. A bit like their city and just like Jesus they will rise from the grave to a greater and everlasting glory and magnificence.