If you want to have a nice spawn but are worried that people might grief it then use this plugin. It prevents block placing. If you want one to prevent breaking of blocks get this plugin also from me.

Comands:
/blockplace <enable/disable> - Toggles placing blocks for all players.
/bp - <enable/disable> - Toggles placing blocks for all players.
/toggleblockplace - <enable/disable> - Toggles placing blocks for all players. players.

Permmsions:
noblockplace.toggle.command

Note all players including ops will not be able to place blocks. If you wish to edit your server, then close your server then do so with a whilist on. This prevents others from join while you make changes.

!!WARNING!!
There is NO config file meaning Restarting/Reloading your server will automatically make blocks not placeable

https://youtube.com/mjdawson